(19)
(11)EP 2 707 135 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
26.06.2019 Bulletin 2019/26

(21)Application number: 12781937.3

(22)Date of filing:  11.05.2012
(51)International Patent Classification (IPC): 
B01J 20/10(2006.01)
B01J 20/24(2006.01)
B01J 20/28(2006.01)
C01B 33/12(2006.01)
C09K 19/38(2006.01)
B01J 20/22(2006.01)
B01J 20/30(2006.01)
B01J 20/283(2006.01)
C09K 19/02(2006.01)
C09K 19/52(2006.01)
(86)International application number:
PCT/CA2012/000457
(87)International publication number:
WO 2012/151688 (15.11.2012 Gazette  2012/46)

(54)

MESOPOROUS SILICA AND ORGANOSILICA FREE-STANDING FILM MATERIALS

FREISTEHENDE MESOPORÖSE SILICA- UND ORGANOSILICA FILM-MATERIALIEN

MATÉRIAUX MÉSOPOREUX EN SILICE ET EN SILICE ORGANIQUE SOUS FORME DE FILMS DÉGAGÉS


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 12.05.2011 US 201161485207 P

(43)Date of publication of application:
19.03.2014 Bulletin 2014/12

(73)Proprietor: FPInnovations
Pointe-Claire, Québec H9R 3J9 (CA)

(72)Inventors:
  • MACLACHLAN, Mark, John
    Vancouver, British Columbia V6J 2A1 (CA)
  • SHOPSOWITZ, Kevin, Eric
    West Vancouver, British Columbia V7V 3H7 (CA)
  • HAMAD, Wadood, Yasser
    Vancouver, British Columbia V6J 2G2 (CA)

(74)Representative: Green, Mark Charles et al
Urquhart-Dykes & Lord LLP Euston House 24 Eversholt Street
London NW1 1AD
London NW1 1AD (GB)


(56)References cited: : 
EP-A1- 1 748 032
WO-A1-2010/110998
WO-A1-2011/123929
US-A1- 2011 248 214
EP-A1- 2 030 949
WO-A1-2010/141426
US-A1- 2004 024 076
  
  • DUJARDIN E ET AL: "Synthesis of mesopporous silica by sol-gel mineralisation of cellulose nanorod nematic suspensions", JOURNAL OF MATERIALS CHEMISTRY, ROYAL SOCIETY OF CHEMISTRY, GB, vol. 13, 1 January 2003 (2003-01-01), pages 696-699, XP002990919, ISSN: 0959-9428, DOI: 10.1039/B212689C
  • KEVIN E. SHOPSOWITZ ET AL: "Free-standing mesoporous silica films with tunable chiral nematic structures", NATURE, vol. 468, no. 7322, 18 November 2010 (2010-11-18), pages 422-425, XP055137543, ISSN: 0028-0836, DOI: 10.1038/nature09540
  • DUJARDIN, E. ET AL.: 'Synthesis of mesoporous silica by sol-gel mineralisation of cellulose nanorod nematic suspensions' J. MATER. CHEM. vol. 13, no. ISSUE, 2003, pages 696 - 699, XP002990919
  
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description

TECHNICAL FIELD



[0001] The present invention relates to mesoporous siliceous materials and a process for their preparation, more especially the invention provides a new method for removing cellulose, especially nanocrystalline cellulose from silica or organosilica composites using strong acids. This gives access to novel mesoporous silica and organosilica materials that may be obtained as free-standing films with or without chiral nematic structures.

BACKGOUND ART



[0002] Porous materials have been extensively studied and are used for a wide range of applications, including as ion exchangers and drying agents.1,2 Porous materials constructed using organic templates do not usually have accessible porosity until the template is removed. For example, mesoporous silica (MCM-41), first reported in 1992, is prepared by templating the condensation of silica around a lyotropic liquid crystalline phase followed by calcination of the template.3-5 Besides calcination, other methods have been used to remove neutral or charged organic or inorganic templates from inside of a porous silica-based material, including acid-extraction and solvent-extraction.6-8 In particular, methods such as solvent extraction and acid-extraction are used to prepare mesoporous organosilicas since the organic group in the wall of the material cannot usually withstand the high temperature conditions of the calcination.9-11 Mesoporous organosilica materials can exhibit unique properties compared to mesoporous silica such as enhanced hydrothermal stability, chemical stability, and mechanical properties.12,13 This class of materials is therefore of great interest for a variety of potential applications.

[0003] Cellulose has been used in various forms to construct cellulose-silica composites.14-16 Where it has been removed to afford a porous structure, the cellulose has been calcined under air or oxygen. We recently reported a new type of silica-cellulose composite material where nanocrystalline cellulose is organized in a chiral nematic assembly inside of the composite.17 After calcination, the nanocrystalline cellulose is decomposed, leaving a porous, chiral nematic silica material. One drawback of this method is that the pores in the material are smaller than the diameter of the individual NCC crystallites owing to condensation and collapse of the pores during calcination. Another significant drawback is that it does not allow for the incorporation of organic groups or other temperature-sensitive groups into the silica walls as they generally will thermally decompose at the temperatures required to degrade cellulose.

[0004] The decomposition of cellulose by a strong acid (e.g., HCl, H2SO4) in water, ionic liquids and other solvents has been extensively studied.18-20 Much of this research has been aimed at converting cellulose to glucose, which may then be converted to ethanol for use as a biofuel. Under these circumstances the conditions must be selected very carefully to avoid the formation of other byproducts of cellulose decomposition. Acid-catalyzed hydrolysis of cellulose has not been applied to the removal of cellulose from silica-cellulose or organosilica-cellulose composite materials, where it can generate properties distinct from those where the cellulose was calcined. In this case, the specific degradation products of cellulose are relatively unimportant so long as the cellulosic material is effectively removed from the silica or organosilica network without structural damage to the network.

DISCLOSURE OF THE INVENTION



[0005] This invention seeks to provide new siliceous mesoporous materials.

[0006] This invention also seeks to provide a process for preparing siliceous mesoporous materials.

[0007] In accordance with one aspect of the invention there is provided a process of producing a mesoporous siliceous free-standing film material comprising: acid hydolysis of cellulose in a siliceous composite selected from the group consisting of silica/nanocrystalline cellulose composites and organosilica/nanocrystalline cellulose composites to produce a mesoporous siliceous material from which nanocrystalline cellulose has been removed by said acid hydolysis.

[0008] In accordance with another aspect of the invention there is provided a mesoporous organosilica having chiral nematic order in the form of a free-standing film.

BRIEF DESCRIPTION OF THE DRAWINGS



[0009] 

FIG. 1: is a UV-Vis-NIR transmission spectrum of NCC-silica composite from preparation 1.

FIG. 2: is a UV-Vis-NIR transmission spectrum of silica from preparation 2.

FIG. 3: is an IR spectrum of silica from preparation 2.

FIG. 4: is a graph of the thermogravimetric analysis (TGA) data of silica from preparation 2.

FIG. 5: is a plot of the N2 adsorption-desorption isotherm of silica from preparation 2.

FIG. 6: is a plot of the BJH pore size distribution (desorption) of silica from preparation 2.

FIG. 7: is a UV-Vis-NIR transmission spectrum of silica from preparation 3.

FIG. 8: is an IR spectrum of silica from preparation 3.

FIG. 9: is a graph of the TGA data of silica from preparation 3.

FIG. 10: is a plot of the N2 adsorption-desorption isotherm of silica from preparation 3.

FIG. 11: is a plot of the BJH (Barret-Joyner-Halenda model) pore size distribution (desorption) of silica from preparation 3.

FIG. 12: is an SEM image of silica from preparation 3.

FIG. 13: is an SEM image of silica from preparation 3 at higher magnification.

FIG. 14: is a UV-Vis-NIR transmission spectrum of silica from preparation 4.

FIG. 15: is a plot of the N2 adsorption-desorption isotherm of silica from preparation 4.

FIG. 16: is a plot of the BJH pore size distribution (desorption) of silica from preparation 4.

FIG. 17: is a IR spectrum of silica from preparation 4.

FIG. 18: is a graph of the TGA data of silica from preparation 4.

FIG. 19: is a UV-Vis-NIR transmission spectrum of silica from preparation 5.

FIG. 20: is a plot of the N2 adsorption-desorption isotherm of silica from preparation 5.

FIG. 21: is a plot of the BJH pore size distribution (desorption) of silica from preparation 5.

FIG. 22: is a UV-Vis-NIR transmission spectrum of organosilica-NCC composite from preparation 6.

FIG. 23: is a UV-Vis-NIR transmission spectrum of organosilica from preparation 7.

FIG. 24: is an IR spectrum of organosilica from preparation 7.

FIG. 25: is a graph of the TGA data of organosilica from preparation 7.

FIG. 26: is a plot of the N2 adsorption-desorption isotherm of organosilica from preparation 7.

FIG. 27: is a plot of the BJH pore size distribution (desorption) of organosilica from preparation 7.

FIG. 28: is an SEM image of organosilica from preparation 7.

FIG. 29: is an SEM image of organosilica from preparation 7 at higher magnification.

FIG. 30: is a UV-Vis-NIR transmission spectrum of organosilica-NCC composite from preparation 8.

FIG. 31: UV-Vis-NIR transmission spectrum of organosilica from preparation 9.


DETAILED DESCRIPTION OF THE INVENTION



[0010] A new process for generating mesoporous materials from organosilica/NCC and silica/NCC composites (where NCC is nanocrystalline cellulose) by removing the NCC using acidic solutions has been developed. This gives rise to mesoporous materials that may be obtained as free-standing films with chiral nematic organization. Compared to the prior art processes that use high temperature treatments to remove NCC, this process yields materials with larger mesopores. Furthermore, it gives access to the first examples of mesoporous organosilicas templated by NCC, which cannot generally be synthesized through calcination due to the thermal or oxidative sensitivity of the organic groups.

[0011] This process allows for a completely novel material to be synthesized, namely mesoporous organosilica templated by cellulose, which cannot be synthesized by calcination of an organosilica/NCC composite material. Furthermore the process results in mesoporous siliceous materials exhibiting higher peak pore diameter as compared with corresponding mesoporous siliceous materials produced under conditions of calcination for removal of NCC. The mesoporous materials may be produced as films which may have chiral or achiral structure. In the case of films with chiral nematic structure, such structure results in iridescence, the color of which may be tuned by changing the ratio of organosilica precursor to NCC. This provides the first example of mesoporous organosilicas with chiral nematic structures.

[0012] The disclosure also allows for preparation of silica-NCC and organosilica-NCC composites that do not have the chiral nematic structure, the acid treatment method described herein may be applied to such materials to afford porous silica or organosilica with or without chiral nematic organization. The combination of porosity and optical properties in these materials makes them interesting for a wide range of applications. The invention employs a new method for the removal of cellulose from silica/NCC or organosilica/NCC composites using aqueous acids that leads to mesoporous silica or organosilica materials. These new mesoporous materials have significantly different properties compared to the corresponding materials obtained when the NCC is removed by calcination. This process enables the development of materials with temperature-sensitive components that would be degraded during thermal decomposition of the NCC. Also, it enables access to different pore sizes than those obtained from thermal decomposition of NCC. In particular, by utilizing acid hydrolysis of NCC from chiral nematic organosilica/NCC composites, novel mesoporous organosilica materials with chiral nematic structures can be prepared. Nitrogen adsorption isotherms show that the materials obtained have high surface areas and porosity. These novel materials are attractive for many practical applications, including catalyst supports (possibly including enantioselective transformations), stationary phases (for separation of chiral or achiral substances), optical filters, sensors, insulators, adsorbents, membranes, and as templates for other chiral nanomaterials. The invention provides the process to remove NCC from silica/NCC or organosilica/NCC composites, as well as the novel materials obtained after removal of the NCC, including both chiral nematic and achiral structures. The acid hydroysis in the process of the invention is typically carried out with maintenance of pores of a volume corresponding to the volume of the composite occupied by the nanocrystalline cellulose (NCC). In particular the composite comprises a siliceous matrix surrounding a skeleton of NCC crystals in which the crystals occupy a volume in the composite defining potential mesopores, i.e. the mesopores left after removal of the cellulose by the acid hydrolysis.

[0013] In particular the mesopores have a peak pore diameter higher than that of a corresponding mesoporous siliceous material produced by calcination of cellulose of the composite and more especially have mesopores with a peak pore diameter of at least 5 nm, and typically 5 to 15 nm.

[0014] The acid hydrolysis is typically carried out with a concentrated acid, for example hydrochloric acid, sulphuric acid, nitric acid or trifluoromethanesulfonic acid. The acid concentration should generally be greater than 3M and more usually greater than 6M. In the case of hydrochloric acid it is especially preferred to have a concentration of 10 to 12M and more especially about 12M. In the case of sulphuric acid a concentration of 4M to 8M and especially about 6M is preferred.

[0015] Nanocrystalline cellulose (NCC) is extracted as a colloidal suspension by acid hydrolysis of cellulosic materials, derived from sources such as bacteria, cotton, and wood pulp. NCC is made from cellulose, a linear polymer of β(1→4) linked D-glucose units, the chains of which arrange themselves to form crystalline and amorphous domains. The NCC is extracted by selectively hydrolyzing the amorphous regions leaving behind the highly crystalline NCC. NCC is characterized by high crystallinity (between 85 and 97%, typically greater than 95%) approaching the theoretical limit of the cellulose chains.

[0016] Colloidal suspensions of cellulose crystallites form a chiral nematic structure upon reaching a critical concentration. The chiral nematic structure of NCC suspensions may be preserved upon evaporation, resulting in chiral nematic films where the helicoidal axis is oriented perpendicular to the surface of the films. These films are visibly iridescent when the helical pitch is on the order of the wavelengths of visible light.

[0017] A broad range of silica and organosilica precursors, e.g. of the general types Si(OR)4, Si(OR1)3R, and Si(OR1)3R2Si(OR3)3, and mixtures thereof in which each R, R1 and R3 may be the same or different and is typically a phenyl group (C6H5), a substituted phenyl group, an alkyl group, a branched alkyl group, a cycloalkane, or any similar organic component, and R2 is a bridging organic component, such as 1,4-phenylene (C6H4), methylene (CH2), ethylene (CH2CH2), propylene (CH2CH2CH2), or any other linear or branched alkylene spacer (e.g., (CH2)6), may be condensed in the presence of NCC to form organosilica/NCC or silica/NCC composite materials. Under appropriate conditions, these composite materials may be obtained as free-standing or self-supporting films with long-range chiral nematic structures. In the present invention, organosilica/NCC and silica/NCC composite materials are subjected to different acidic conditions in order to obtain mesoporous materials, which may be obtained as free-standing films with long-range chiral nematic structures.

[0018] The removal of NCC from free-standing chiral nematic silica/NCC composite films (Preparation 1) may be successfully carried out with inorganic acids, for example hydrochloric acid, sulfuric acid, or nitric acid, or mixtures thereof. Treatment of the films in concentrated acid in water is typically at elevated temperatures in the range of 70 °C to 120 °C. Acid hydrolysis with hydrochloric acid in water (12 M) at elevated temperatures (preferably >80 °C) and ambient pressure causes decomposition of the NCC within the composite films (when concentrated HCI is used at lower concentrations or temperatures, NCC degradation does not appear to occur). Free-standing mesoporous silica films are obtained after filtration and washing with water (Preparation 2). Initially colorless films with a reflectance peak (measured by UV-visible spectroscopy) at 1260 nm (FIG. 1) owing to the chiral nematic structure of the films appear light to dark brown after the HCI treatment due to the formation of insoluble cellulose decomposition products. A reflection peak is apparent in the dry films at 700 nm (FIG. 2) demonstrating that the chiral nematic structure is retained in the films after the acid treatment. The blue-shift in the reflectance peak is consistent with the decrease in refractive index that occurs due to cellulose removal. The infrared (IR) spectrum (FIG. 3) of the product obtained from Preparation 2 confirms that cellulose decomposition has occurred. However, as indicated by the brown color of the films and thermogravimetric analysis (TGA) (FIG. 4), residual organic material (22 wt. %) with a decomposition temperature of ∼400 °C is still present in the material. Nitrogen adsorption measurements reveal a type IV isotherm with hysteresis demonstrating that the films are mesoporous (BET, Brunauer-Emmett-Teller model, surface area = 470 m2/g, FIG. 5). Significantly, the pore diameter is considerably larger than the analogous materials prepared by calcination of the silica-NCC composite material. The BJH (Barret-Joyner-Halenda model) pore size distribution shows a peak pore diameter of 7 nm (FIG. 6). (The peak pore diameter for samples prepared directly by calcination is typically < 4 nm.)

[0019] The residual organic material may be removed from the films using oxidizing conditions (Preparation 3). When the brown mesoporous films are placed in a 4:1 mixture of sulfuric acid and hydrogen peroxide (30% in water), the color rapidly disappears. After washing the films with water and drying, the films regain their iridescence and show a reflectance peak at 680 nm (FIG. 7) that is attributed to the chiral nematic structure. The reflectance peak is located at essentially the same position that was observed before the oxidizing treatment; however, it is much more distinct due to the removal of the brown organic contaminants. IR spectroscopy (FIG. 8) and TGA (FIG. 9) confirm that the oxidizing treatment is able to successfully remove the residual cellulose decomposition products from the films. Elemental analysis reveals only trace amounts of carbon after the oxidizing treatment (<0.3 wt. %). Nitrogen adsorption shows that this treatment does not substantially affect the porosity of the materials, with the isotherm (FIG. 10) and BJH pore size distribution (FIG. 11) essentially unchanged. The specific pore volume is slightly increased, which is consistent with the removal of residual organic material from the mesopores. Scanning electron microscopy (SEM) provides further evidence that long range chiral nematic order is maintained in the mesoporous silica obtained using Preparation 3 (FIG. 12). At higher magnification the rod-like morphology of NCC imprinted into the silica (FIG. 13) is observed. The mesoporous silica is therefore an accurate replica of the NCC template. This demonstrates that this procedure is able to selectively remove NCC without causing structural damage to the silica.

[0020] Sulfuric acid may also be employed to remove NCC from the composite films. Treatment of the composite films in 6-9 M sulfuric acid at > 80 °C (Preparation 4) also results in slightly brown mesoporous silica films. The reflection peak observed in the UV-vis spectrum (690 nm, FIG. 14) is very similar to that observed for preparations 2 and 3; however, the porosity (FIGS. 15-16) measured for Preparation 4 is somewhat different. While the peak BJH pore diameter is very similar (∼7 nm) the BET surface area (750 m2/g) is considerably higher than that measured for preparations 2 and 3. IR spectroscopy (FIG. 17) and TGA (FIG. 18) reveal that considerably less residual cellulosic decomposition products remain in the films compared to when concentrated HCl is used. Sulfuric acid/hydrogen peroxide can also be successfully used to completely remove any remaining insoluble cellulosic decomposition products from Preparation 4.

[0021] Concentrated nitric acid at 85 °C (Preparation 5) also removes NCC from the composite films. However, the reflectance peak (from the chiral nematic structure) and porosity measured for this sample are considerably different than those measured for Preparations 2, 3, and 4. The reflectance peak for Preparation 5 is blue-shifted compared to Preparations 2 and 4 and occurs at 560 nm (FIG. 19). The BET surface area measured for the material obtained from Preparation 5 is still high (450 m2/g), but the shape of the N2 adsorption/desorption isotherm (type I/IV hybrid) indicates that there is a large micropore contribution to the surface area (FIG. 20). The BJH pore size-distribution gives a sharp peak at 3.5 nm (FIG. 21), which is approximately half the diameter of those calculated for Preparations 2-4. It therefore appears that in contrast to hydrochloric acid and sulphuric acid, nitric acid causes structural damage to the mesoporous silica framework. This may be avoidable by adjusting the concentration and temperature employed in the procedure.

[0022] Organosilica-NCC composite films were prepared using 1,2-bis(triethoxysilyl)-ethane as the organosilica precursor (Preparations 6 and 8). Preparation 6 gives free-standing films with a chiral nematic structure as indicated by a reflectance peak at 620 nm (FIG. 22) in the UV-visible spectrum. These films were studied to determine whether acid hydrolysis can be used to generate mesoporous organosilica from organosilica-NCC composites; i.e., whether NCC can be selectively removed from the composite without decomposition of the organosilica. The composite material was subjected to concentrated HCl at 85 °C followed by brief treatment with H2SO4/hydrogen peroxide (Preparation 7) in order to ensure complete removal of NCC and any cellulosic decomposition products. This treatment results in somewhat flexible, iridescent, free-standing films. After cellulose removal, the reflectance peak in the UV-visible spectrum is shifted to 450 nm (Fig. 23). IR spectroscopy, TGA, and elemental analysis confirm that the cellulose is removed with retention of the ethylene bridge in the organosilica. The IR spectrum (FIG. 24) shows peaks at 1270 cm-1 and 690 cm-1 corresponding to Si-C symmetric deformation and stretching respectively, while two peaks corresponding to CH2 stretching modes are seen at 2895 cm-1 and 2930 cm-1. From TGA, a 20% wt. loss is observed at 450 °C (FIG. 25), matching very closely to the theoretical value of 21% based on the loss of C2H4 from a material with the chemical formula C2H4O3Si2. Elemental analysis gives a value of 17.3% carbon, which is again very close to the theoretical value of 18.2% based on the above formula. N2 adsorption shows the organosilica to be mesoporous with a very similar isotherm to that measured for the mesoporous silica prepared using the same procedure (FIG. 26). Indeed the BET surface area (460 m2/g) and peak pore size (7 nm, FIG. 27) are virtually identical to the values calculated for the mesoporous silica prepared using the same conditions (Preparation 3). SEM images show a chiral nematic structure that is an accurate replica of the NCC template (FIGS. 28-29). Generally, the free-standing mesoporous organosilica films appear similar to the corresponding mesoporous silica films, however, the organosilica films are considerably less brittle and more flexible. These superior mechanical properties could be advantageous for certain applications.

[0023] An additional mesoporous organosilica sample was prepared in order to demonstrate that the color of the films can be tuned in the same way as chiral nematic mesoporous silica films (i.e., by varying the ratio of NCC and silica precursor). Preparation 8 is identical to Preparation 6 except that a higher ratio of 1,2-bis(triethoxysilyl)-ethane was used relative to NCC. As expected, the reflectance peak for this sample is red-shifted (λmax = 820 nm) compared to the sample prepared in Preparation 6 (FIG. 30). Following the same procedure as Preparation 7, the NCC from the composite films may be removed while leaving the organosilica intact, resulting in mesoporous organosilica films with a peak reflectance of 680 nm (Preparation 9, FIG. 31). The color of the mesoporous organosilica films may therefore be tuned by varying the ratio of organosilica precursor to NCC used in the synthesis. Preparations 10 through 19 show further examples of organosilica/NCC composites and the corresponding mesoporous organosilica materials, all with chiral nematic organization as evidenced by iridescence and a reflection peak in the UV-visible/near-IR spectrum. These illustrate that the organic component in the matrix may be varied to obtain the chiral nematic organosilica/NCC composites and mesoporous organosilica materials.

[0024] Thus, in accordance with the invention NCC may be selectively removed from silica/NCC or organosilica/NCC composites using acid-catalyzed hydrolysis. The vast literature of pre-treatment methods that are known to improve the efficiency of acid-catalyzed cellulose hydrolysis (e.g. hydrothermal, ozonolysis, etc.) should also be applicable to the process of the invention, given the stabilities of silica and organosilica materials. For both silica and organosilica, the resulting mesoporous materials may be obtained as free-standing chiral nematic films with larger mesopores than the corresponding materials obtained by calcination. This process allows for a completely novel material to be synthesized, namely mesoporous organosilica templated by NCC, which cannot be synthesized by calcination of an organosilica-NCC composite material. The chiral nematic structure of these films results in iridescence, the color of which may be tuned by changing the ratio of organosilica precursor to NCC. Silica-NCC and organosilica-NCC composites can also be prepared that do not have the chiral nematic structure, the acid treatment method described herein may be applied to such materials to afford porous silica or organosilica with or without chiral nematic organization. The combination of porosity and optical properties in these materials makes them interesting for a wide range of applications.

EXAMPLES



[0025] In the Examples, sonication was applied to ensure that the NCC particles were dispersed. The sonicator was a standard laboratory model (2 A, 120 V) available from VWR (Aquasonic model 50T - trademark). A sonication time of 10-15 minutes was typically applied prior to addition of the silicon-containing compound.

Preparation 1



[0026] 4 mL of tetramethoxysilane (TMOS) is added to 100 mL of a freshly sonicated 3.5% aqueous suspension of NCC. The mixture is stirred for 1 h at 20 °C and then poured into polystyrene Petri dishes to evaporate. The resulting colorless films are peeled off of the substrate to obtain free-standing composite films with a reflectance peak at 1260 nm (FIG. 1).

Preparation 2



[0027] Silica/NCC composite films from preparation 1 (411 mg) are added to 500 mL of 12 M HCI and heated to 85 °C for 18 h. After cooling to room temperature, the reaction mixture is poured into 1 L of water and filtered. The recovered films are washed with water and after drying, 216 mg of light brown/iridescent films with a reflectance peak at 700 nm (FIG. 2) are obtained. The IR spectrum (FIG. 3) and TGA (FIG. 4) of the sample show that NCC decomposition has occurred with some residual organic material remaining in the films. N2 adsorption measurements (Fig. 5) give a BET surface area of 470 m2/g and a specific pore volume of 0.68 cm3/g.

Preparation 3



[0028] Mesoporous silica films from preparation 2 (150 mg) are placed in 100 mL of 4:1 H2SO4/hydrogen peroxide (30%) until the films are completely colorless (∼5 min). The reaction mixture is poured into 1 L of water and filtered. The recovered films are washed with water and after drying, 120 mg of iridescent films with a reflectance peak at 680 nm (FIG. 7) are obtained. The IR spectrum (FIG. 8), elemental analysis, and TGA (FIG. 9) of the sample show that all organic material has been removed. N2 adsorption measurements (FIG. 10) give a BET surface area of 450 m2/g and a specific pore volume of 0.77 cm3/g.

Preparation 4



[0029] Silica/NCC composite films from preparation 1 (400 mg) are added to 160 mL of 9M H2SO4 and heated to 85 °C for 18 h. After cooling to room temperature, the reaction mixture is poured into 1 L of water and filtered. The recovered films are washed with water and after drying, 160 mg of mostly colorless iridescent films with a reflectance peak at 680 nm (FIG. 14) are obtained. The IR spectrum (FIG. 17) and TGA (FIG. 18) of the sample show that the NCC has been removed from the films. N2 adsorption measurements (FIG. 15) give a BET surface area of 750 m2/g and a specific pore volume of 0.92 cm3/g.

Preparation 5



[0030] Silica/NCC composite films from preparation 1 (400 mg) are added to 160 mL of concentrated nitric acid and heated to 85 °C for 18 h. After cooling to room temperature, the reaction mixture is poured into 1 L of water and filtered. The recovered films are washed with water and after drying, 130 mg of iridescent films with a reflectance peak at 560 nm (FIG. 19) are obtained. The IR spectrum and TGA of the sample show that the NCC has been removed from the films. N2 adsorption measurements (FIG. 20) give a BET surface area of 450 m2/g and a specific pore volume of 0.30 cm3/g.

Preparation 6



[0031] 1.28 mL of 1,2-bis(triethoxysilyl)-ethane is added to 20 mL of a freshly sonicated 3% aqueous suspension of NCC. The mixture is stirred for 3 h at 90 °C and then left stirring at 20 °C for 18 h. The reaction mixture is microfiltered (0.45 µm) and poured into polystyrene Petri dishes to evaporate. The resulting iridescent films are peeled off of the substrate to obtain free-standing composite films with a reflectance peak at 620 nm (FIG. 22).

Preparation 7



[0032] Organosilica/NCC composite films from preparation 6 (360 mg) are placed in 400 mL of 12 M HCI and heated to 85 °C for 18 h. After cooling to room temperature, the reaction mixture is poured into 1 L of water and filtered. After washing with water and drying, the slightly brown iridescent films are placed in 50 mL of 4:1 H2SO4/H2O2 (30%) until the films are completely colorless (∼2-3 min). The reaction mixture is poured into 500 mL of water, filtered, and washed with water. After air-drying, 160 mg of iridescent films with a reflection peak at 450 nm (FIG. 23) are obtained. IR spectroscopy (FIG. 24), TGA (FIG. 25), and elemental analysis confirm that the cellulose is removed with retention of the ethylene bridge in the organosilica. N2 adsorption measurements (FIG. 26) give a BET surface area of 460 m2/g and a specific pore volume of 0.73 cm3/g.

Preparation 8



[0033] 1.70 mL of 1,2-bis(triethoxysilyl)-ethane is added to 20 mL of a freshly sonicated 3% aqueous suspension of NCC. The mixture is stirred for 3 h at 90 °C and then left stirring at 20 °C for 18 h. The reaction mixture is microfiltered (0.45 µm) and poured into polystyrene Petri dishes to evaporate. The resulting iridescent films are peeled off of the substrate to obtain free-standing composite films with a reflectance peak at 820 nm (FIG. 30).

Preparation 9



[0034] Organosilica/NCC composite films from preparation 8 (584 mg) are placed in 400 mL of 12 M HCI and heated to 85 °C for 18 h. After cooling to room temperature, the reaction mixture is poured into 1 L of water and filtered. After washing with water and drying, the slightly brown iridescent films are placed in 50 mL of 4:1 H2SO4/H2O2 (30%) until the films are completely colorless (∼2-3 min). The reaction mixture is poured into 500 mL of water, filtered, and washed with water. After air-drying, 270 mg of iridescent films with a reflection peak at 680 nm (FIG. 31) are obtained. IR spectroscopy, TGA, and elemental analysis confirm that the cellulose is removed with retention of the ethylene bridge in the organosilica. N2 adsorption measurements give a BET surface area of 498 m2/g and a specific pore volume of 0.80 cm3/g.

Preparation 10



[0035] 0.5 mL of 1,2-bis(trimethoxysilyl)-ethane is added to 15 mL of 3.5% aqueous NCC. The mixture is stirred for 2 h at room temperature. The reaction mixture is poured into polystyrene Petri dishes to evaporate. The resulting iridescent films are peeled off of the substrate to obtain free-standing composite films with a reflectance peak at ∼1160 nm.

Preparation 11



[0036] Organosilica/NCC composite films from preparation 10 are placed in 6M H2SO4 and heated to 100 °C for 20 hours. After cooling to room temperature, the reaction mixture was filtered and alternately washed with a solution of piranha (20 mL 30% H2O2 / 100 mL H2SO4) and water until colorless. The films were then washed with water and allowed to air-dry. 130 mg of the iridescent films with a reflection peak at ∼720 nm are obtained. IR spectroscopy and TGA confirmed that the cellulose is removed with retention of the ethylene bridge in the organosilica. N2 adsorption measurements indicate a mesoporous material with a BET surface area of 594 m2/g and a specific pore volume of 0.87 cm3/g.

Preparation 12



[0037] 0.47 mL of 1,2-bis(triethoxysilyl)-methane is added to 10 mL of 3.5% aqueous NCC and 4 mL of ethanol. The mixture is stirred for 2 h at room temperature. The reaction mixture is poured into polystyrene Petri dishes to evaporate. The resulting iridescent films are peeled off of the substrate to obtain free-standing composite films with a reflectance peak at ∼1215 nm.

Preparation 13



[0038] Organosilica/NCC composite films from preparation 12 are placed in 6M H2SO4 and heated to 100°C for 20 hours. After cooling to room temperature, the reaction mixture was filtered and alternately washed with a solution of piranha (20 mL 30% H2O2 / 100 mL H2SO4) and water until colorless. The films were then washed with water and allowed to air-dry. 101 mg of the iridescent films with a reflection peak at ∼670 nm are obtained. IR spectroscopy, TGA, and elemental analysis confirmed that the cellulose is removed with retention of the methylene bridge in the organosilica. N2 adsorption measurements show the material is mesoporous with a BET surface area of 518 m2/g and a specific pore volume of 0.54 cm3/g.

Preparation 14



[0039] 1.2 mL of 1,4-bis(triethoxysilyl)-benzene is added to 35 mL of freshly sonicated 3.5% aqueous NCC and 35 mL of ethanol. The mixture is stirred for 2 h at room temperature. The reaction mixture is poured into polystyrene Petri dishes to evaporate. The resulting iridescent films are peeled off of the substrate to obtain free-standing composite films with a reflectance peak at ∼1470 nm.

Preparation 15



[0040] Organosilica/NCC composite films from preparation 14 are placed in concentrated HCI and heated to 90 °C for 20 hours. The films were filtered, washed with water and placed in a solution of hydrogen peroxide (30%, 20 mL) and silver nitrate (0.013 g) at 90°C for 2 hours. The films were then filtered, placed in water and heated to 70 °C overnight. The films were filtered and allowed to air-dry. 73 mg of the iridescent films with a reflection peak at -665 nm are obtained. IR spectroscopy and TGA confirmed that the cellulose is removed with retention of the benzene bridge in the organosilica.

Preparation 16



[0041] 0.24 mL of 1,2-bis(trimethoxysilyl)-ethane and 0.13 mL of 1,6-bis(trimethoxysilyl)-hexane is added to 10.2 mL of 3.5% aqueous NCC. The mixture is stirred for 2 h at room temperature. The reaction mixture is poured into polystyrene Petri dishes to evaporate. The resulting iridescent films are peeled off of the substrate to obtain free-standing composite films with a reflectance peak at ∼1215 nm.

Preparation 17



[0042] Organosilica/NCC composite films from preparation 16 are placed in 6M H2SO4 and heated to 100°C for 20 hours. After cooling to room temperature, the reaction mixture was filtered and alternately washed with a solution of piranha (20 mL 30% H2O2 / 100 mL H2SO4) and water until colorless. The films were then washed with water and allowed to air-dry. 70 mg of the iridescent films with a reflection peak at 700-750 nm are obtained. IR spectroscopy, TGA, and elemental analysis confirmed that the cellulose is removed with retention of the ethylene and hexane bridges in the organosilica. N2 adsorption measurements indicate that the material is mesoporous with a BET surface area of 467 m2/g and a specific pore volume of 0.78 cm3/g.

Preparation 18



[0043] 0.47 mL of 1,2-bis(trimethoxysilyl)-ethane and 0.32 mL of 1,4-bis(triethoxysilyl)-benzene is added to 20 mL of freshly sonicated 3.5% aqueous NCC and 20 mL of ethanol. The mixture is stirred for 2 h at room temperature. The reaction mixture is poured into polystyrene Petri dishes to evaporate. The resulting iridescent films are peeled off of the substrate to obtain free-standing composite films with a reflectance peak at ∼1445 nm.

Preparation 19



[0044] Organosilica/NCC composite films from preparation 18 are placed in concentrated HCI and heated to 80°C for 20 hours. The films were filtered, washed with water and placed in a solution of hydrogen peroxide (30%, 20 mL) and silver nitrate (0.015 g) at 70°C for 2 hours. The films were then filtered, placed in water and heated to 70 °C overnight. The films were filtered and allowed to air-dry. 145 mg of the iridescent films with a reflection peak at 1000-1100 nm are obtained. IR spectroscopy, TGA, and elemental analysis confirmed that the cellulose is removed with retention of the ethylene and benzene bridges in the organosilica. N2 adsorption measurements indicate that the product is mesoporous with a BET surface area of 684 m2/g and a specific pore volume of 1.07 cm3/g.

References



[0045] 
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  8. 8. Zhao, D.Y., Feng, J.L., Huo, Q.S., Chmelka, B.F. & Stucky, G.D. Nonionic triblock and star diblock copolymer and oligomeric surfactant syntheses of highly ordered, hydrothermally stable, mesoporous silica structures. J. Am. Chem. Soc. 120, 6024-6036 (1998).
  9. 9. Asefa, T., MacLachlan, M.J., Coombs, N. & Ozin, G.A. Periodic mesoporous organosilicas with organic groups inside the channel walls. Nature 402, 867-871 (1999).
  10. 10. Inagaki, S., Guan, S., Ohsuna, T. & Terasaki, O. An ordered mesoporous organosilica hybrid material with a crystal-like wall structure. Nature 416, 304-307 (2002).
  11. 11. Asefa, T., Kruk, M., MacLachlan, M.J., Coombs, N., Grondey, H., Jaroniec, M. & Ozin, G.A. Novel bifunctional periodic mesoporous organosilicas, BPMOs: Synthesis, characterization, properties and in-situ selective hydroboration-alcoholysis reactions of functional groups. J. Am. Chem. Soc. 123, 8520-8530 (2001).
  12. 12. Lu, Y., Fan, H., Doke, N., Loy, D.A., Assink, R.A., LaVan, D.A. & Brinker C.J. Evaporation-induced self-assembly of hybrid bridged silsesquioxane film and particulate mesophases with integral organic functionality. J. Am. Chem. Soc. 122, 5258-5261 (2000).
  13. 13. Burleigh, M.C., Markowitz, M.A., Jayasundera, S., Spector, M.S., Thomas, C.W. & Gaber, B.P. Mechanical and hydrothermal stabilities of aged periodic mesoporous organosilicas. J. Phys. Chem. B 107, 12628-12634 (2003).
  14. 14. Dujardin, E., Blaseby, M. & Mann, S. Synthesis of mesoporous silica by sol-gel mineralisation of cellulose nanorod nematic suspensions. J. Mater. Chem. 13, 696-699 (2003).
  15. 15. Thomas, A. & Antonietti, M. Silica nanocasting of simple cellulose derivatives: towards chiral pore systems with long-range order and chiral optical coatings. Adv. Funct. Mater. 13, 763-766 (2003).
  16. 16. Wang, W., Liu, R., Liu, W., Tan, J., Liu, W., Kang, H. & Huang, Y. Hierarchical mesoporous silica prepared from ethyl-cyanoethyl cellulose cholesteric liquid crystalline phase. J. Mater. Sci. 45, 5567-5573 (2010).
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  18. 18. Mosier, N., Wyman, C., Dale, B., Elander, R., Lee, Y.Y., Holtzapple, M. & Ladisch M. Features of promising technologies for pretreatment of lignocellulosic biomass. Bioresource Technology 96, 673-686 (2005).
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Claims

1. A process of producing a mesoporous siliceous free-standing film material having chiral nematic order comprising:
acid hydrolysis of cellulose in a siliceous composite selected from the group consisting of silica/nanocrystalline cellulose composites and organosilica/nanocrystalline cellulose composites to produce a mesoporous siliceous material having chiral nematic order from which nanocrystalline cellulose has been removed by said acid hydrolysis.
 
2. A process according to claim 1, wherein said acid hydrolysis is carried out with a concentrated inorganic acid in water at a temperature of 70 °C to 120 °C; wherein said concentrated acid is hydrochloric acid, sulphuric acid, nitric acid or trifluoromethanesulfonic acid, wherein said concentrated acid is greater than 3M and preferably greater than 6M.
 
3. A process according to claim 2, wherein said concentrated acid is hydrochloric acid at a concentration of 10M to 12M, and said temperature is >80 °C.
 
4. A process according to claim 2, wherein said concentrated acid is sulphuric acid at concentration of 4M to 8M.
 
5. A process according to any one of claims 1 to 4, including a step of removing residual cellulose and products of cellulose hydrolysis from said mesoporous siliceous material, after said acid hydrolysis, by oxidising said residual cellulose and products of cellulose hydrolysis.
 
6. A process according to any one of claims 1 to 5, wherein said composite comprises a siliceous matrix surrounding a skeleton of nanocrystalline cellulose crystals, said crystals, said skeleton having chiral nematic order and occupying a volume in the composite defining potential mesopores.
 
7. A mesoporous organosilica having chiral nematic order in the form of a free-standing film.
 
8. A mesoporous organosilica according to claim 7, comprising a mesoporous organosilica matrix having mesopores with a peak pore diameter of at least 5 nm, preferably 5 nm to 15 nm.
 


Ansprüche

1. Verfahren zur Herstellung eines mesoporösen silicatischen freistehenden Filmmaterials mit chiraler nematischer Ordnung, umfassend:
Säurehydrolyse von Cellulose in einem silicatischen Verbundstoff ausgewählt aus der Gruppe bestehend aus Silica-/Nanokristalline-Cellulose-Verbundstoffen und Organosilica-/Nanokristalline-Cellulose-Verbundstoffen, um ein mesoporöses silicatisches Material mit chiraler nematischer Ordnung zu erzeugen, aus dem nanokristalline Cellulose durch die Säurehydrolyse entfernt worden ist.
 
2. Verfahren gemäß Anspruch 1, wobei die Säurehydrolyse mit einer konzentrierten anorganischen Säure in Wasser bei einer Temperatur von 70 °C bis 120 °C durchgeführt wird; wobei die konzentrierte Säure Salzsäure, Schwefelsäure, Salpetersäure oder Trifluormethansulfonsäure ist, wobei die konzentrierte Säure mehr als 3 M und vorzugsweise mehr als 6 M ist.
 
3. Verfahren gemäß Anspruch 2, wobei die konzentrierte Säure Salzsäure mit einer Konzentration von 10 M bis 12 M ist und die Temperatur > 80 °C beträgt.
 
4. Verfahren gemäß Anspruch 2, wobei die konzentrierte Säure Schwefelsäure mit einer Konzentration von 4 M bis 8 M ist.
 
5. Verfahren gemäß einem der Ansprüche 1 bis 4, umfassend einen Schritt des Entfernens von restlicher Cellulose und Cellulosehydrolyseprodukten aus dem mesoporösen silicatischen Material nach der Säurehydrolyse durch Oxidieren der restlichen Cellulose und der Cellulosehydrolyseprodukte.
 
6. Verfahren gemäß einem der Ansprüche 1 bis 5, wobei der Verbundstoff eine silicatische Matrix umfasst, die ein Skelett von nanokristallinen Cellulosekristallen umgibt, wobei das Skelett chirale nematische Ordnung aufweist und ein Volumen in dem Verbundstoff besetzt, das potentielle Mesoporen definiert.
 
7. Mesoporöses Organosilica mit chiraler nematischer Ordnung in der Form eines freistehenden Films.
 
8. Mesoporöses Organosilica gemäß Anspruch 7, umfassend eine mesoporöse Organosilicamatrix mit Mesoporen mit einem Scheitelwert des Porendurchmessers von wenigstens 5 nm, vorzugsweise 5 nm bis 15 nm.
 


Revendications

1. Procédé de production d'un matériau siliceux mésoporeux sous forme de film autoportant ayant un ordre nématique chiral comprenant :
l'hydrolyse acide de cellulose dans un composite siliceux choisi dans le groupe constitué par les composites silice/cellulose nanocristalline et les composites silice organique/cellulose nanocristalline pour produire un matériau siliceux mésoporeux ayant un ordre nématique chiral duquel la cellulose nanocristalline a été retirée par ladite hydrolyse acide.
 
2. Procédé selon la revendication 1, dans lequel ladite hydrolyse acide est réalisée avec un acide inorganique concentré dans l'eau à une température de 70 °C à 120 °C ; ledit acide concentré étant l'acide chlorhydrique, l'acide sulfurique, l'acide nitrique ou l'acide trifluorométhanesulfonique, ledit acide concentré étant plus de 3M et de préférence plus de 6M.
 
3. Procédé selon la revendication 2, dans lequel ledit acide concentré est l'acide chlorhydrique à une concentration de 10M à 12M, et ladite température est > 80 °C.
 
4. Procédé selon la revendication 2, dans lequel ledit acide concentré est l'acide sulfurique à une concentration de 4M à 8M.
 
5. Procédé selon l'une quelconque des revendications 1 à 4, comportant une étape de retrait de la cellulose résiduelle et des produits d'hydrolyse de la cellulose dudit matériau siliceux mésoporeux, après ladite hydrolyse acide, par oxydation de ladite cellulose résiduelle et desdits produits d'hydrolyse de la cellulose.
 
6. Procédé selon l'une quelconque des revendications 1 à 5, dans lequel ledit composite comprend une matrice siliceuse entourant un squelette de cristaux de cellulose nanocristalline, ledit squelette ayant un ordre nématique chiral et occupant un volume dans le composite définissant des mésopores potentiels.
 
7. Silice organique mésoporeuse ayant un ordre nématique chiral sous la forme d'un film autoportant.
 
8. Silice organique mésoporeuse selon la revendication 7, comprenant une matrice de silice organique mésoporeuse ayant des mésopores avec un diamètre maximal de pores d'au moins 5 nm, de préférence de 5 nm à 15 nm.
 




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Cited references

REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description




Non-patent literature cited in the description