CN110938211B - Method for modifying cellulose nanocrystal by using photo-response fluorine-containing amphiphilic block copolymer - Google Patents
Method for modifying cellulose nanocrystal by using photo-response fluorine-containing amphiphilic block copolymer Download PDFInfo
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Abstract
The invention discloses a method for modifying cellulose nanocrystals by using a photoresponse fluorine-containing amphiphilic block copolymer, which is implemented according to the following steps: step 1, preparing a hydrophilic acrylate polymer; step 2, preparing a hydrophilic acrylate copolymer containing epoxy groups; step 3, preparing a fluorine-containing amphiphilic block copolymer; step 4, preparing a pure photoresponse fluorine-containing amphiphilic block copolymer; and 5, preparing the photoresponse fluorine-containing amphiphilic block copolymer modified cellulose nanocrystal. The invention overcomes the problems of strong hydrophilicity and easy agglomeration of the cellulose nanocrystal and endows the material with the characteristic of photoresponse.
Description
Technical Field
The invention belongs to the technical field of grafting modification of the surface of a nano particle, and particularly relates to a method for modifying a cellulose nanocrystal by using a photoresponse fluorine-containing amphiphilic block copolymer.
Background
In recent years, with the importance of environmental protection and the shortage of petrochemical resources, it has been fully recognized that cellulose nanocrystals are superior to petroleum and natural gas resources with limited reserves. The cellulose nanocrystal not only has the characteristics of renewability, lightweight property, degradability, biocompatibility and the like commonly possessed by biological materials, but also has the characteristics of large specific surface area, excellent mechanical property, high crystallinity, high Young modulus and the like, so that the cellulose nanocrystal has great application prospects in the fields of papermaking, foods, medicines, coatings, polymer composite materials and the like. The nanocellulose crystal has large polarity and specific surface area, so that the nanocellulose crystal has the problems of agglomeration, poor compatibility with a matrix and the like when being used as a reinforcing agent of a composite material. In order to solve the above problems, it is necessary to functionally modify the cellulose nanocrystals to improve the performance thereof. In addition, the modification can endow the cellulose nanocrystal with some new characteristics on the basis of not changing the original properties of the cellulose nanocrystal. The research on the modification of the cellulose nanocrystals includes surface adsorption modification, surface hydroxyl chemical modification and graft copolymerization modification of the cellulose nanocrystals, and the modification modes are widely developed at home and abroad.
The grafting modification of the cellulose nanocrystal mainly utilizes hydroxyl on the surface of the cellulose nanocrystal as a grafting point, and combines a polymer through a chemical bond to form a graft copolymerization product, so that the dispersibility of the cellulose nanocrystal can be improved, and more functions can be given to the cellulose nanocrystal. At present, the grafting modification method of the cellulose nanocrystal mainly comprises traditional living radical polymerization, Atom Transfer Radical Polymerization (ATRP), nitrogen-oxygen living radical polymerization (NMP), reversible addition fragmentation chain transfer (RAFT) polymerization, ring-opening polymerization and the like. RAFT polymerization has been widely used to prepare polymer materials having a specific structure due to the advantages of a wide range of monomers to be polymerized, mild polymerization conditions, and a high ability to design molecules. At present, polymers containing functional groups and block copolymers are mainly prepared by a RAFT method.
The coumarin unit has good light response performance, and can generate reversible photocrosslinking and photolysis polymerization. The coumarin group can be grafted to the surface of the cellulose nanocrystal through graft copolymerization modification, the cellulose nanocrystal modified by the coumarin derivative is compounded with other materials, the mechanical property of the material is enhanced, meanwhile, the material can be endowed with good photoresponsive performance, and under the irradiation of ultraviolet light, the modified cellulose nanocrystal can be used as a crosslinking site to carry out photocrosslinking reaction, so that the structure of the material is regulated and controlled, and the application prospect in the fields of light control films, drug sustained release and self-repair and the like is wide.
Disclosure of Invention
The invention aims to provide a method for modifying cellulose nanocrystals by using a photoresponse fluorine-containing amphiphilic block copolymer, which overcomes the problems of strong hydrophilicity and easy agglomeration of the cellulose nanocrystals and endows the material with photoresponse characteristics.
The technical scheme adopted by the invention is that the method for modifying the cellulose nanocrystal by the photo-response fluorine-containing amphiphilic block copolymer is implemented according to the following steps:
step 1, preparing a hydrophilic acrylate polymer;
step 2, preparing a hydrophilic acrylate copolymer containing epoxy groups;
step 3, preparing a fluorine-containing amphiphilic block copolymer;
step 4, preparing a pure photoresponse fluorine-containing amphiphilic block copolymer;
and 5, preparing the photoresponse fluorine-containing amphiphilic block copolymer modified cellulose nanocrystal.
The invention is also characterized in that:
the specific process of the step 1 is as follows:
at room temperature, sequentially mixing a small molecular RAFT reagent, an initiator, a hydrophilic acrylate monomer and a solvent according to a mass ratio of 20-100: 4-25: 350-1600: 1050-4800 adding into a four-neck flask; introducing argon for 20-30 min while magnetically stirring; heating to 65-80 ℃, and reacting for 6-8 h; to obtain the hydrophilic acrylate polymer.
The small molecular RAFT reagent adopts S-1-dodecyl-S ' - (alpha, alpha ' -dimethyl-alpha ' -acetic acid) trithiocarbonate or isopropyl phenyl dithiobenzoate;
the solvent adopts 1, 4-dioxane, benzene or N, N-dimethylformamide;
the hydrophilic acrylate monomer is: 2- (dimethylamino) ethyl methacrylate, 2- (dimethylamino) ethyl methacrylate or 2- (diisopropylamino) ethyl methacrylate;
the initiator is azobisisobutyronitrile or azobisisoheptonitrile;
the four-mouth flask is provided with a reflux condenser pipe, an air duct and a thermometer.
The specific process of the step 2 is as follows:
adding an initiator, an epoxy group-containing ethylene monomer and a solvent into the four-neck flask containing the hydrophilic acrylate polymer obtained in the step (1) according to the mass ratio of 1-14, 100-350 and 300-1050 in sequence; introducing argon for 20-30 min while magnetically stirring; heating to 70-85 ℃, and reacting for 6-8 h; to obtain the hydrophilic acrylate copolymer containing epoxy groups.
The solvent adopts 1, 4-dioxane, benzene or N, N-dimethylformamide;
the epoxy group-containing ethylene monomer is glycidyl methacrylate or glycidyl acrylate;
the initiator is azobisisobutyronitrile or azobisisoheptonitrile.
The specific process of the step 3 is as follows:
sequentially mixing an initiator, a fluorine-containing acrylate monomer and a solvent according to a mass ratio of 1-14: 450 to 2250: 1350-6750 adding the four-neck flask containing the hydrophilic acrylate copolymer containing the epoxy group obtained in the step 2; introducing argon for 20-30 min while magnetically stirring; heating to 80-90 ℃, and reacting for 6-8 h; to obtain the fluorine-containing amphiphilic block copolymer.
The solvent adopts 1, 4-dioxane, benzene or N, N-dimethylformamide;
the fluorine-containing acrylate monomer is 2, 2, 2-trifluoroethyl methacrylate, hexafluorobutyl acrylate or hexafluorobutyl methacrylate;
the initiator is azobisisobutyronitrile or azobisisoheptonitrile.
The specific process of the step 4 is as follows:
sequentially mixing an initiator, a coumarin-based vinyl monomer and a solvent according to a mass ratio of 1-14: 400-2000: 1200-6000 adding the fluorine-containing amphiphilic block copolymer obtained in the step (3) into a four-neck flask; introducing argon for 20-30 min while magnetically stirring; heating to 85-90 ℃, and reacting for 6-8 h; obtaining a photoresponse fluorine-containing amphiphilic block copolymer; precipitating and purifying the photoresponse fluorine-containing amphiphilic block copolymer in normal hexane; and drying the precipitate in a vacuum oven for 3-4 h to obtain the pure photoresponse fluorine-containing amphiphilic block copolymer.
The solvent adopts 1, 4-dioxane, benzene or N, N-dimethylformamide;
the coumarin-based vinyl monomer is 7- (2-acrylate ethoxy) -4-methylcoumarin, 7- (4-acrylate butoxy) -4-methylcoumarin, or 7- (4-vinylbenzyloxy) -4-methylcoumarin;
the initiator is azobisisobutyronitrile or azobisisoheptonitrile.
The specific process of the step 5 is as follows:
sequentially mixing a photoresponse fluorine-containing amphiphilic block copolymer, cellulose nanocrystals, N-dimethylformamide and a catalyst according to a mass ratio of 4-8: 1-4: 100-150: 1-3 adding the mixture into a three-neck flask provided with a reflux condenser pipe; heating to 100 ℃ and 150 ℃, and reacting for 48-60 h; centrifuging the product, washing the precipitate with tetrahydrofuran for 2-3 times, and vacuum drying at 40-50 ℃; obtaining the photoresponse fluorine-containing amphiphilic block copolymer modified cellulose nanocrystal.
The catalyst is as follows: triethylamine, pyridine or N, N-diisopropylethylamine.
The invention has the beneficial effects that:
(1) in the preparation method of the photoresponse fluorine-containing amphiphilic block copolymer modified cellulose nanocrystal, a reversible addition-fragmentation chain transfer polymerization (RAFT) method is adopted to synthesize the photoresponse fluorine-containing amphiphilic block copolymer for modifying the cellulose nanocrystal, wherein a hydrophilic acrylate monomer is used as a hydrophilic monomer, a fluorine-containing acrylate monomer is used as a hydrophobic monomer, and a coumarin-based vinyl monomer is used as a photoresponse monomer;
(2) in the preparation method of the photoresponse fluorine-containing amphiphilic block copolymer modified cellulose nanocrystal, the photoresponse fluorine-containing amphiphilic block copolymer reacts with hydroxyl on the cellulose nanocrystal through the active epoxy group, and the photoresponse fluorine-containing amphiphilic block copolymer is grafted to the surface of the cellulose nanocrystal, so that the problems of strong hydrophilicity and easy agglomeration of the cellulose nanocrystal are solved, the photoresponse characteristic is endowed, and the application performance of the cellulose nanocrystal is effectively improved.
Drawings
FIG. 1 is a photo-response spectrum of a photo-response fluorine-containing amphiphilic block copolymer of the present invention;
FIG. 2 is a photoresponse spectrum of cellulose nanocrystal modified by the photoresponse fluorine-containing amphiphilic block copolymer.
Detailed Description
The present invention will be described in detail with reference to the following embodiments.
The method for modifying the cellulose nanocrystal by the photoresponse fluorine-containing amphiphilic block copolymer is implemented according to the following steps:
step 1, preparing a hydrophilic acrylate polymer;
the specific process of the step 1 is as follows:
at room temperature, sequentially mixing a small molecular RAFT reagent, an initiator, a hydrophilic acrylate monomer and a solvent according to a mass ratio of 20-100: 4-25: 350-1600: 1050-4800 adding into a four-neck flask; introducing argon for 20-30 min; heating to 65-80 ℃, and stirring for reaction for 6-8 h; obtaining a hydrophilic acrylate polymer;
the small molecular RAFT reagent adopts S-1-dodecyl-S ' - (alpha, alpha ' -dimethyl-alpha ' -acetic acid) trithiocarbonate or isopropyl phenyl dithiobenzoate;
the solvent adopts 1, 4-dioxane, benzene or N, N-dimethylformamide;
the hydrophilic acrylate monomer is: 2- (dimethylamino) ethyl methacrylate, 2- (dimethylamino) ethyl methacrylate or 2- (diisopropylamino) ethyl methacrylate;
the initiator is azobisisobutyronitrile or azobisisoheptonitrile;
the four-mouth flask is provided with a reflux condenser pipe, an air duct and a thermometer.
Step 2, preparing a hydrophilic acrylate copolymer containing epoxy groups;
the specific process of the step 2 is as follows:
adding an initiator, an epoxy group-containing ethylene monomer and a solvent into the four-neck flask containing the hydrophilic acrylate polymer obtained in the step (1) according to the mass ratio of 1-14, 100-350 and 300-1050 in sequence; introducing argon for 20-30 min; heating to 70-85 ℃, and stirring for reaction for 6-8 h; obtaining hydrophilic acrylate copolymer containing epoxy groups;
the solvent adopts 1, 4-dioxane, benzene or N, N-dimethylformamide;
the epoxy group-containing ethylene monomer is glycidyl methacrylate or glycidyl acrylate;
the initiator is azobisisobutyronitrile or azobisisoheptonitrile.
Step 3, preparing a fluorine-containing amphiphilic block copolymer;
the specific process of the step 3 is as follows:
sequentially mixing an initiator, a fluorine-containing acrylate monomer and a solvent according to a mass ratio of 1-14: 450 to 2250: 1350-6750 adding the four-neck flask containing the hydrophilic acrylate copolymer containing the epoxy group obtained in the step 2; introducing argon for 20-30 min; heating to 80-90 ℃, and stirring for reaction for 6-8 h; obtaining a fluorine-containing amphiphilic block copolymer;
the solvent adopts 1, 4-dioxane, benzene or N, N-dimethylformamide;
the fluorine-containing acrylate monomer is 2, 2, 2-trifluoroethyl methacrylate, hexafluorobutyl acrylate or hexafluorobutyl methacrylate;
the initiator is azobisisobutyronitrile or azobisisoheptonitrile.
Step 4, preparing a pure photoresponse fluorine-containing amphiphilic block copolymer;
sequentially mixing an initiator, a coumarin-based vinyl monomer and a solvent according to a mass ratio of 1-14: 400-2000: 1200-6000 adding the fluorine-containing amphiphilic block copolymer obtained in the step (3) into a four-neck flask; introducing argon for 20-30 min; heating to 85-90 ℃, and stirring for reaction for 6-8 h; obtaining a photoresponse fluorine-containing amphiphilic block copolymer; precipitating and purifying the photoresponse fluorine-containing amphiphilic block copolymer in normal hexane; drying the precipitate in a vacuum oven for 3-4 h to obtain a pure photoresponse fluorine-containing amphiphilic block copolymer;
the solvent adopts 1, 4-dioxane, benzene or N, N-dimethylformamide;
the coumarin-based vinyl monomer is 7- (2-acrylate ethoxy) -4-methylcoumarin, 7- (4-acrylate butoxy) -4-methylcoumarin, or 7- (4-vinylbenzyloxy) -4-methylcoumarin;
the initiator is azobisisobutyronitrile or azobisisoheptonitrile.
Step 5, preparing photoresponse fluorine-containing amphiphilic block copolymer modified cellulose nanocrystalline;
the specific process of the step 5 is as follows:
sequentially mixing a photoresponse fluorine-containing amphiphilic block copolymer, cellulose nanocrystals, N-dimethylformamide and a catalyst according to a mass ratio of 4-8: 1-4: 100-150: 1-3 adding the mixture into a three-neck flask provided with a reflux condenser pipe; heating to 100 ℃ and 150 ℃, and reacting for 48-60 h; centrifuging the product, washing the precipitate with tetrahydrofuran for 2-3 times, and vacuum drying at 40-50 ℃; obtaining the photoresponse fluorine-containing amphiphilic block copolymer modified cellulose nanocrystal.
The catalyst is as follows: triethylamine, pyridine or N, N-diisopropylethylamine.
Example 1
Step 1, at room temperature, sequentially mixing 20: 4: 350: 1050S-1-dodecyl-S ' - (alpha, alpha ' -dimethyl-alpha ' -acetic acid) trithiocarbonate, azobisisobutyronitrile, N-dimethylaminoethyl methacrylate and 1, 4-dioxane are added into a four-neck flask provided with a reflux condenser, a gas guide tube and a thermometer; introducing argon for 20min, heating to 65 ℃, and stirring for reacting for 6h to obtain poly N, N-dimethylaminoethyl methacrylate;
step 2, sequentially setting the mass ratio as 1: 100: 300 of azodiisobutyronitrile, glycidyl methacrylate and 1, 4-dioxane are added into the four-neck flask containing the poly N, N-dimethylaminoethyl methacrylate obtained in the step 1; introducing argon for 20min, heating to 70 ℃, and stirring for reacting for 6h to obtain poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate);
and 3, sequentially setting the mass ratio as 1: 450: 1350 of azodiisobutyronitrile, hexafluorobutyl acrylate and 1, 4-dioxane, and the mixture is added into the four-neck flask containing poly N, N-dimethylaminoethyl methacrylate-b-poly glycidyl methacrylate obtained in the step 2; introducing argon for 20min, heating to 80 ℃, and stirring for reacting for 6h to obtain poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate) -b-poly (hexafluorobutyl acrylate);
and 4, sequentially setting the mass ratio as 1: 400: 1200, adding azodiisobutyronitrile, 7- (4-vinylbenzyloxy) -4-methylcoumarin and 1, 4-dioxane into the four-neck flask containing poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate) -b-poly (hexafluorobutyl acrylate) obtained in the step (3); introducing argon for 20min, heating to 85 ℃, and stirring for reacting for 6h to obtain poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate) -b-poly (hexafluorobutyl acrylate) -b-poly (7- (4-vinylbenzyloxy) -4-methylcoumarin;
precipitating the synthesized poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate) -b-poly (hexafluorobutyl acrylate) -b-poly (7- (4-vinylbenzyloxy) -4-methylcoumarin) in N-hexane, and drying the precipitate in a vacuum oven for 3h to obtain pure poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate) -b-poly (hexafluorobutyl acrylate) -b-poly (7- (4-vinylbenzyloxy) -4-methylcoumarin);
and 5, sequentially setting the mass ratio as 4: 1: 100: 1, adding pure poly N, N-dimethylaminoethyl methacrylate-b-poly glycidyl methacrylate-b-poly hexafluorobutyl acrylate-b-poly 7- (4-vinylbenzyloxy) -4-methylcoumarin, cellulose nanocrystal, N-dimethylformamide and pyridine into a three-neck flask provided with a reflux condenser tube; heating to 100 ℃, reacting for 48h, centrifuging the product, washing the precipitate with tetrahydrofuran for 3 times, and drying in vacuum at 40 ℃ to obtain the photoresponse fluorine-containing amphiphilic block copolymer modified cellulose nanocrystal.
Example 2
Step 1, sequentially mixing 50 parts by mass: 15: 1250: 3750S-1-dodecyl-S ' - (alpha, alpha ' -dimethyl-alpha ' -acetic acid) trithiocarbonate, azobisisobutyronitrile, N-dimethylaminoethyl methacrylate, into a four-neck flask equipped with a reflux condenser, a gas-guide tube and a thermometer; introducing argon for 25min, heating to 70 ℃, and stirring for reaction for 7h to obtain poly N, N-dimethylaminoethyl methacrylate;
step 2, sequentially setting the mass ratio as 5: 175: 525 adding azodiisobutyronitrile, glycidyl methacrylate and N, N-dimethylaminoethyl methacrylate into the four-neck flask filled with the N, N-dimethylaminoethyl methacrylate obtained in the step 1; introducing argon for 25min, heating to 80 ℃, and stirring for reacting for 8h to obtain poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate);
and 3, sequentially setting the mass ratio as 7: 2100: 6300 azobisisobutyronitrile, hexafluorobutyl acrylate, and N, N-dimethylaminoethyl methacrylate, added to the four-necked flask containing N, N-dimethylaminoethyl methacrylate-b-polyglycidyl methacrylate obtained in step 2; introducing argon for 25min, heating to 85 ℃, and stirring for reaction for 7h to obtain poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate) -b-poly (hexafluorobutyl acrylate);
and 4, sequentially setting the mass ratio as 9: 1500: 4500 of azobisisobutyronitrile, 7- (4-vinylbenzyloxy) -4-methylcoumarin, and N, N-dimethylaminoethyl methacrylate, adding into the four-neck flask containing N, N-dimethylaminoethyl methacrylate-b-polyglycidyl methacrylate-b-hexafluorobutyl acrylate obtained in the step 3; introducing argon for 25min, heating to 85 ℃, and stirring for reaction for 7h to obtain poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate) -b-poly (hexafluorobutyl acrylate) -b-poly (7- (4-vinylbenzyloxy) -4-methylcoumarin;
precipitating the synthesized poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate) -b-poly (hexafluorobutyl acrylate) -b-poly (7- (4-vinylbenzyloxy) -4-methylcoumarin) in N-hexane, and drying the precipitate in a vacuum oven for 4h to obtain pure poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate) -b-poly (hexafluorobutyl acrylate) -b-poly (7- (4-vinylbenzyloxy) -4-methylcoumarin);
and 5, sequentially setting the mass ratio as 6: 2: 120: 2, adding pure poly N, N-dimethylaminoethyl methacrylate-b-poly glycidyl methacrylate-b-poly hexafluorobutyl acrylate-b-poly 7- (4-vinylbenzyloxy) -4-methylcoumarin, cellulose nanocrystal, N-dimethylformamide and pyridine into a three-neck flask provided with a reflux condenser, heating to 120 ℃, reacting for 55h, centrifuging the product, washing the precipitate with tetrahydrofuran for 3 times, and drying in vacuum at 40 ℃ to obtain the photoresponse fluorine-containing amphiphilic block copolymer modified cellulose nanocrystal.
Example 3
Step 1, sequentially mixing 100 parts by mass: 25: 1600: 4800 adding S-1-dodecyl-S ' - (alpha, alpha ' -dimethyl-alpha ' -acetic acid) trithiocarbonate, azobisisobutyronitrile, and benzene into a four-neck flask equipped with reflux condenser, gas-guide tube, and thermometer; introducing argon for 30min, heating to 80 ℃, and stirring for reacting for 8h to obtain poly N, N-dimethylaminoethyl methacrylate;
step 2, sequentially setting the mass ratio as 14: 350: 1050 azodiisobutyronitrile, glycidyl methacrylate and benzene are added into the four-neck flask containing the N, N-dimethylaminoethyl methacrylate obtained in the step 1; introducing argon for 30min, heating to 85 ℃, and stirring for reacting for 8h to obtain poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate);
and 3, sequentially setting the mass ratio as 14: 2250: 6750 azodiisobutyronitrile, hexafluorobutyl acrylate, and benzene are added into the four-neck flask containing poly (N, N-dimethylaminoethyl methacrylate-b-poly (glycidyl methacrylate) obtained in step 2; introducing argon for 30min, heating to 90 ℃, and stirring for reacting for 8h to obtain poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate) -b-poly (hexafluorobutyl acrylate);
and 4, sequentially setting the mass ratio as 14: 2000: 6000 azodiisobutyronitrile, 7- (4-vinylbenzyloxy) -4-methylcoumarin and benzene are added into the four-neck flask containing poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate) -b-poly (hexafluorobutyl acrylate) obtained in the step (3); introducing argon for 30min, heating to 90 ℃, and stirring for reacting for 8h to obtain poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate) -b-poly (hexafluorobutyl acrylate) -b-poly (7- (4-vinylbenzyloxy) -4-methylcoumarin;
precipitating the synthesized poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate) -b-poly (hexafluorobutyl acrylate) -b-poly (7- (4-vinylbenzyloxy) -4-methylcoumarin) in N-hexane, and drying the precipitate in a vacuum oven for 4h to obtain pure poly (N, N-dimethylaminoethyl methacrylate) -b-poly (glycidyl methacrylate) -b-poly (hexafluorobutyl acrylate) -b-poly (7- (4-vinylbenzyloxy) -4-methylcoumarin);
and 5, sequentially setting the mass ratio as 8: 4: 150: 3, adding pure poly N, N-dimethylaminoethyl methacrylate-b-poly glycidyl methacrylate-b-poly hexafluorobutyl acrylate-b-poly 7- (4-vinylbenzyloxy) -4-methylcoumarin, cellulose nanocrystal, N-dimethylformamide and pyridine into a three-neck flask provided with a reflux condenser, heating to 150 ℃, reacting for 60 hours, centrifuging the product, washing the precipitate with tetrahydrofuran for 3 times, and drying in vacuum at 50 ℃ to obtain the photoresponse fluorine-containing amphiphilic block copolymer modified cellulose nanocrystal.
FIG. 1 is a photoresponse spectrum of a photoresponse amphiphilic block copolymer; FIG. 2 is a photoresponse spectrum of cellulose nanocrystalline modified by the photoresponse fluorine-containing amphiphilic block copolymer.
As can be seen from FIG. 1, under the irradiation of 365nm ultraviolet light, the absorption peak intensity of the photo-responsive fluorine-containing amphiphilic triblock copolymer at 321nm gradually decreases with the increase of the illumination time (FIG. 1 a); subsequently, under the irradiation of 254nm ultraviolet light, the intensity of an absorption peak at 321nm is gradually increased along with the increase of time (fig. 1b), and the photoresponse characteristics of the coumarin functional group of the synthesized photoresponse amphiphilic block copolymer are proved;
fig. 2 also demonstrates that the modified cellulose nanocrystals have photoresponse properties.
In conclusion, the invention adopts RAFT polymerization technology to prepare the photoresponse fluorine-containing amphiphilic triblock copolymer, and successfully grafts the photoresponse fluorine-containing amphiphilic triblock copolymer to the surface of the cellulose nanocrystal, thereby endowing the cellulose nanocrystal with photoresponse characteristics.
Claims (5)
1. The method for modifying the cellulose nanocrystal by the photo-response fluorine-containing amphiphilic block copolymer is characterized by comprising the following steps:
step 1, preparing a hydrophilic acrylate polymer; the specific process of the step 1 is as follows: at room temperature, sequentially mixing a small molecular RAFT reagent, an initiator, a hydrophilic acrylate monomer and a solvent according to a mass ratio of 20-100: 4-25: 350-1600: 1050-4800 adding into a four-neck flask; introducing argon for 20-30 min; heating to 65-80 ℃, and stirring for reaction for 6-8 h; obtaining a hydrophilic acrylate polymer;
step 2, preparing a hydrophilic acrylate copolymer containing epoxy groups; the specific process of the step 2 is as follows: adding an initiator, an epoxy group-containing ethylene monomer and a solvent into the four-neck flask containing the hydrophilic acrylate polymer obtained in the step (1) according to the mass ratio of 1-14, 100-350 and 300-1050 in sequence; introducing argon for 20-30 min; heating to 70-85 ℃, and stirring for reaction for 6-8 h; obtaining hydrophilic acrylate copolymer containing epoxy groups;
step 3, preparing a fluorine-containing amphiphilic block copolymer; the specific process of the step 3 is as follows: sequentially mixing an initiator, a fluorine-containing acrylate monomer and a solvent according to a mass ratio of 1-14: 450 to 2250: 1350-6750 adding the four-neck flask containing the hydrophilic acrylate copolymer containing the epoxy group obtained in the step 2; introducing argon for 20-30 min; heating to 80-90 ℃, and stirring for reaction for 6-8 h; obtaining a fluorine-containing amphiphilic block copolymer;
step 4, preparing a pure photoresponse fluorine-containing amphiphilic block copolymer; the specific process of the step 4 is as follows: sequentially mixing an initiator, a coumarin-based vinyl monomer and a solvent according to a mass ratio of 1-14: 400-2000: 1200-6000 adding the fluorine-containing amphiphilic block copolymer obtained in the step (3) into a four-neck flask; introducing argon for 20-30 min; heating to 85-90 ℃, and stirring for reaction for 6-8 h; obtaining a photoresponse fluorine-containing amphiphilic block copolymer; precipitating and purifying the photoresponse fluorine-containing amphiphilic block copolymer in normal hexane; drying the precipitate in a vacuum oven for 3-4 h to obtain a pure photoresponse fluorine-containing amphiphilic block copolymer;
step 5, preparing photoresponse fluorine-containing amphiphilic block copolymer modified cellulose nanocrystalline; the specific process of the step 5 is as follows:
sequentially mixing a photoresponse fluorine-containing amphiphilic block copolymer, cellulose nanocrystals, N-dimethylformamide and a catalyst according to a mass ratio of 4-8: 1-4: 100-150: 1-3 adding the mixture into a three-neck flask provided with a reflux condenser pipe; heating to 100 ℃ and 150 ℃, and reacting for 48-60 h; centrifuging the product, washing the precipitate with tetrahydrofuran for 2-3 times, and vacuum drying at 40-50 ℃; obtaining a photoresponse fluorine-containing amphiphilic block copolymer modified cellulose nanocrystal; the catalyst is as follows: triethylamine, pyridine or N, N-diisopropylethylamine.
2. The method for modifying cellulose nanocrystals according to claim 1, wherein the small molecule RAFT reagent employs S-1-dodecyl-S' - (α, α "-dimethyl- α" -acetic acid) trithiocarbonate or cumyl dithiobenzoate;
the solvent adopts 1, 4-dioxane, benzene or N, N-dimethylformamide;
the hydrophilic acrylate monomer is: 2- (dimethylamino) ethyl methacrylate, 2- (dimethylamino) ethyl methacrylate or 2- (diisopropylamino) ethyl methacrylate;
the initiator is azobisisobutyronitrile or azobisisoheptonitrile;
the four-mouth flask is provided with a reflux condenser pipe, an air guide pipe and a thermometer.
3. The method for modifying cellulose nanocrystals by using the photo-responsive fluorine-containing amphiphilic block copolymer as claimed in claim 2, wherein the epoxy group-containing vinyl monomer is glycidyl methacrylate or glycidyl acrylate.
4. The method for modifying cellulose nanocrystals by using the photo-responsive fluorine-containing amphiphilic block copolymer as claimed in claim 3, wherein the fluorine-containing acrylate monomer is 2, 2, 2-trifluoroethyl methacrylate, hexafluorobutyl acrylate or hexafluorobutyl methacrylate.
5. The method for modifying cellulose nanocrystals according to claim 4, wherein the coumarin-based vinyl monomer is 7- (2-acrylate ethoxy) -4-methylcoumarin, 7- (4-acrylate butoxy) -4-methylcoumarin, or 7- (4-vinylbenzyloxy) -4-methylcoumarin.
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