CN100463930C - Redispersable pH-sensitive cation polymer hydrogel sub-micrometer grain and its preparation method - Google Patents
Redispersable pH-sensitive cation polymer hydrogel sub-micrometer grain and its preparation method Download PDFInfo
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- CN100463930C CN100463930C CNB2006101305021A CN200610130502A CN100463930C CN 100463930 C CN100463930 C CN 100463930C CN B2006101305021 A CNB2006101305021 A CN B2006101305021A CN 200610130502 A CN200610130502 A CN 200610130502A CN 100463930 C CN100463930 C CN 100463930C
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Abstract
The invention discloses a dispersible pH sensitive cationic polymer gel sub-micron particle and making method, which comprises the following steps: allocating raw material through non-ion soluble macromolecular monomer, cation monomer, crosslinking agent and initiator weight rate at 20%-70%25%-75% 0.7%-3%0.7%-3%; dissolving in the acetonitrile or alcohol; aerating nitrogen to reflux; evaporating solvent; dripping secondary distill water; cooling dispersing liquid naturally; centrifuging to separate; dialyzing upper supernatant layer; freezing to drying; making the gel sub-micron particle disperse in the pure water, physiological saline and buffer as drug control carrier releasing material.
Description
Technical field
The present invention relates to a kind of Redispersable ph-sensitive cation polymer hydrogel sub-micrometer grain and its preparation method, belong to pH sensitive hydrogel high polymer material technology.
Background technology
Polymer hydrogel sub-micrometer grain is a class submicrometer structure, can swelling in water and undissolved polymer particles.Hydrogel sub-micrometer grain has the characteristics of the environment-responsive of hydrogel, especially has huge application potential and wide application prospect at biomedicine field as fields such as environmental response, biological medicine, biosimulation, biological sense organ, fine materials, artificial-muscle, chemical separations in a lot of fields.
According to the difference of entrained group, hydrogel sub-micrometer grain can be divided into non-ionic type and ionic hydrogel sub-micrometer grain, and the ionic hydrogel sub-micrometer grain is divided into cationic again and the anionic hydrogel sub-micrometer grain; According to environment-responsive, hydrogel sub-micrometer grain is divided into temperature sensitive type water gel sub-micrometer grain, pH sensitive hydrogel sub-micrometer grain and temperature and the dual sensitive hydrogel sub-micrometer grain of pH.
PH sensitive hydrogel sub-micrometer grain generally contains in structure more-COOH ,-NH
2Or-CONH
2Group can be prepared by vinylformic acid (MAA) and derivatives monomer thereof and hydrophobic monomer (as MMA, EMA) copolymerization as the anionic hydrogel sub-micrometer grain, and its pH susceptibility derives from-COOH.Cationic hydrogel sub-micrometer grain is generally the polyalcohol hydrogel that contains amido, and as polyvinylpyridine etc., its pH susceptibility derives from the protonated of amido on the polymer molecular chain.
People often select for use the methacrylic ester or the acrylate that contain amido or ammonium ion to prepare the cationic water gel.Bibliographical information is arranged, and with methacrylic acid-N, it is in the polyvinyl fluoride tube of 4mm that N dimethylamine base ethyl ester, water and linking agent ethylene glycol-double methyl methacrylate adds diameter, adopts radio polymerization finally to obtain oval column type hydrogel.Yet contain the methacrylic ester of amido or ammonium ion or research that acrylate prepares redispersible hydrogel sub-micrometer grain does not appear in the newspapers as yet about employing.
Summary of the invention
The object of the present invention is to provide a kind of Redispersable ph-sensitive cation polymer hydrogel sub-micrometer grain and its preparation method, this hydrogel sub-micrometer grain lyophilized powder can disperse in media such as pure water and swelling in the certain pH scope, having the medicine of negative charge by the electrostatic interaction load, is the excellent carrier material of control drug release; Its preparation method process is simple.
The present invention is realized by the following technical programs, a kind of Redispersable pH-sensitive cation polymer hydrogel sub-micrometer grain, it is characterized in that, the mass content of wetting ability non-ionic polymers part is 20%～70% in this Redispersable pH-sensitive cation polymer hydrogel sub-micrometer grain, the mass content of cationic polymers part is 25%～75%, the mass content of initiator part is 0.7%～3%, and the mass content of linking agent part is 0.7%～3%.
The Redispersable pH-sensitive cation polymer hydrogel sub-micrometer grain preparation method who submits a written statement to a higher authority and state is characterized in that comprising following process:
With non-ionic water-soluble macromonomer and cationic monomer, linking agent and initiator, press mass ratio 20%～70%: 25%～75%: 0.7%～3%: 0.7%～3% adds in the reactor, be dissolved in acetonitrile or the ethanol, logical nitrogen 20min, 80 ℃ of back flow reaction 6h, drip redistilled water in the time of the air distillation organic solvent, the distillation finish after with the dispersion liquid naturally cooling, with the refrigerative dispersion liquid behind centrifugal 15min under the 3000rpm, with the supernatant liquid intercepting relative molecular mass of packing into is the 72h that dialyses in 8000-14400 the dialysis tubing, and the dispersion liquid after the dialysis gets the white powder product through lyophilize.
Above-mentioned non-ionic water-soluble macromonomer, be selected from relative molecular mass and be the methacrylic ester or the acrylate of single end capped polyoxyethylene glycol such as 454～10000 alkyl oxide, alkyl ester, the methacrylic ester or the acrylate of end capped oxyethane of the list of alkyl oxide or alkyl ester and epoxy propane copolymer; Cationic monomer, be selected from methacrylic acid-N, N dimethylamine base ethyl ester or vinylformic acid-N, N dimethylamine base ethyl ester, methacrylic acid-N, N dimethylamine base ethyl ester or vinylformic acid-N, N dimethylamine base ethyl ester, methylacryoyloxyethyl dimethyl octyl group brometo de amonio or acrylyl oxy-ethyl dimethyl octyl group brometo de amonio, methacrylic acid ester quat or quaternary ammonium acrylate, Methacrylamide quaternary ammonium salt or acrylamide quaternary ammonium salt; Linking agent is selected from TEG-double methyl methacrylate, N,N methylene bis acrylamide or Vinylstyrene; Initiator is selected from Diisopropyl azodicarboxylate, 2,2'-Azobis(2,4-dimethylvaleronitrile), dibenzoyl peroxide or di-isopropyl peroxydicarbonate; Solvent is selected from acetonitrile or ethanol.
The invention has the advantages that preparation process is simple, prepared hydrogel sub-micrometer grain energy redispersion is in body fluid, the tissue culture medium of pure water, physiological saline, damping fluid, animals and plants or human body; PH＜7 o'clock, hydrogel sub-micrometer grain generation swelling, and pH〉7 o'clock, the change of size of hydrogel sub-micrometer grain is very little.
Embodiment
With embodiment the present invention further is illustrated again below.
Embodiment 1:
With 1.8848g methacrylic acid-N, N-dimethylaminoethyl, 0.062g TEG-double methyl methacrylate, 0.973g relative molecular mass are that 2080 poly glycol monomethyl ether acrylate and 0.04g Diisopropyl azodicarboxylate, 70mL acetonitrile add in the 100mL four-hole bottle, logical nitrogen 20min, 80 ℃ of back flow reaction 6h; Drip the 10mL redistilled water in the time of the air distillation acetonitrile, the distillation finish after with the dispersion liquid naturally cooling, then with the refrigerative dispersion liquid behind centrifugal 15min under the 3000rpm, with the supernatant liquid intercepting relative molecular mass of packing into is the 72h that dialyses in 8000～14400 the dialysis tubing, and the dispersion liquid after the dialysis gets the white powder product through lyophilize.
The cation polymer hydrogel sub-micrometer grain particle diameter of present embodiment preparation is 295nm, and particle diameter is 647nm after the complete swelling in pure water, and particle diameter reaches maximum when pH=5, is 700nm, is pH under alkaline condition〉change of size was very little 7 o'clock.
Embodiment 2:
With 2.2193g methacrylic acid-N, N-dimethylaminoethyl, 0.0888g TEG-double methyl methacrylate, 0.5918g relative molecular mass are that 2080 poly glycol monomethyl ether acrylate and 0.0592g Diisopropyl azodicarboxylate, 70mL acetonitrile add in the 100mL four-hole bottle, logical nitrogen 20min, 80 ℃ of back flow reaction 6h; Drip the 10mL redistilled water in the time of the air distillation acetonitrile, the distillation finish after with the dispersion liquid naturally cooling, then with the refrigerative dispersion liquid behind centrifugal 15min under the 3000rpm, with the supernatant liquid intercepting relative molecular mass of packing into is the 72h that dialyses in 8000-14400 the dialysis tubing, and the dispersion liquid after the dialysis gets the white powder product through lyophilize.
Embodiment 3:
With 0.7398g methacrylic acid-N, N-dimethylaminoethyl, 0.0592g TEG-double methyl methacrylate, 2.0713g relative molecular mass are that 2080 poly glycol monomethyl ether acrylate and 0.0888g Diisopropyl azodicarboxylate, 70mL acetonitrile add in the 100mL four-hole bottle, logical nitrogen 20min, 80 ℃ of back flow reaction 6h; Drip the 10mL redistilled water in the time of the air distillation acetonitrile, the distillation finish after with the dispersion liquid naturally cooling, then with the refrigerative dispersion liquid behind centrifugal 15min under the 3000rpm, with the supernatant liquid intercepting relative molecular mass of packing into is the 72h that dialyses in 8000-14400 the dialysis tubing, and the dispersion liquid after the dialysis gets the white powder product through lyophilize.
Embodiment 4:
With 1.8848g methacrylic acid-N, N-dimethylaminoethyl, 0.0207g TEG-double methyl methacrylate, 0.9057g relative molecular mass are that 2080 poly glycol monomethyl ether acrylate and 0.0207g Diisopropyl azodicarboxylate, 70mL acetonitrile add in the 100mL four-hole bottle, logical nitrogen 20min, 80 ℃ of back flow reaction 6h; Drip the 10mL redistilled water in the time of the air distillation acetonitrile, the distillation finish after with the dispersion liquid naturally cooling, then with the refrigerative dispersion liquid behind centrifugal 15min under the 3000rpm, with the supernatant liquid intercepting relative molecular mass of packing into is the 72h that dialyses in 8000-14400 the dialysis tubing, and the dispersion liquid after the dialysis gets the white powder product through lyophilize.
Embodiment 5:
Device and operation are with embodiment 1, wherein relative molecular mass is that to change relative molecular mass into be 454 poly glycol monomethyl ether acrylate for 2080 poly glycol monomethyl ether acrylate, methacrylic acid-N, N dimethylamine base ethyl ester changes vinylformic acid-N into, N dimethylamine base ethyl ester, TEG-double methyl methacrylate changes N,N methylene bis acrylamide into, Diisopropyl azodicarboxylate changes 2,2'-Azobis(2,4-dimethylvaleronitrile) into, and acetonitrile changes ethanol into.
Embodiment 6:
Device and operation are with embodiment 1, wherein relative molecular mass is that to change relative molecular mass into be 10000 poly glycol monomethyl ether acrylate for 2080 poly glycol monomethyl ether acrylate, methacrylic acid-N, N dimethylamine base ethyl ester changes methacrylic acid-N into, N dimethylamine base ethyl ester, TEG-double methyl methacrylate changes Vinylstyrene into, and Diisopropyl azodicarboxylate changes dibenzoyl peroxide into.
Embodiment 7:
Device and operation are with embodiment 1, wherein the poly glycol monomethyl ether acrylate changes polyethyleneglycol ether acrylate into, methacrylic acid-N, and N dimethylamine base ethyl ester changes vinylformic acid-N into, N dimethylamine base ethyl ester, Diisopropyl azodicarboxylate changes di-isopropyl peroxydicarbonate into.
Embodiment 8:
Device and operation are with embodiment 1, and wherein the poly glycol monomethyl ether acrylate changes polyethyleneglycol ether methacrylic ester into, and methacrylic acid-N, N dimethylamine base ethyl ester change methylacryoyloxyethyl dimethyl octyl group brometo de amonio into.
Embodiment 9:
Device and operation are with embodiment 1, and wherein the poly glycol monomethyl ether acrylate changes the methacrylic ester of the end capped polyoxyethylene glycol of alkyl ester list into, and methacrylic acid-N, N dimethylamine base ethyl ester change acrylyl oxy-ethyl dimethyl octyl group brometo de amonio into.
Embodiment 10:
Device and operation are with embodiment 1, and wherein the poly glycol monomethyl ether acrylate changes the acrylate of the end capped polyoxyethylene glycol of alkyl ester list into, methacrylic acid-N, and N dimethylamine base ethyl ester changes the methacrylic acid ester quat into.
Embodiment 11:
Device and operation are with embodiment 1, and wherein the poly glycol monomethyl ether acrylate changes the methacrylic ester of end capped oxyethane of alkyl oxide list and epoxy propane copolymer into, methacrylic acid-N, and N dimethylamine base ethyl ester changes quaternary ammonium acrylate into.
Embodiment 12:
Device and operation are with embodiment 1, and wherein the poly glycol monomethyl ether acrylate changes the acrylate of end capped oxyethane of alkyl oxide list and epoxy propane copolymer into, methacrylic acid-N, and N dimethylamine base ethyl ester changes the Methacrylamide quaternary ammonium salt into.
Embodiment 13:
Device and operation are with embodiment 1, and wherein the poly glycol monomethyl ether acrylate changes the methacrylic ester of end capped oxyethane of alkyl ester list and epoxy propane copolymer into, methacrylic acid-N, and N dimethylamine base ethyl ester changes the acrylamide quaternary ammonium salt into.
Embodiment 14:
Device and operation are with embodiment 1, and wherein the poly glycol monomethyl ether acrylate changes the acrylate of end capped oxyethane of alkyl ester list and epoxy propane copolymer into.
Claims (2)
1. the cation polymer hydrogel sub-micrometer grain of redispersible and pH susceptibility, it is characterized in that, the mass content of wetting ability non-ionic polymers part is 20%～70% in the cation polymer hydrogel sub-micrometer grain, and it is 454～10000 poly glycol monomethyl ether acrylate that the non-ionic water-soluble macromonomer is selected from relative molecular mass, polyethyleneglycol ether acrylate, polyethyleneglycol ether methacrylic ester, the methacrylic ester of the end capped polyoxyethylene glycol of alkyl ester list, the acrylate of the end capped polyoxyethylene glycol of alkyl ester list, the methacrylic ester of end capped oxyethane of alkyl oxide list and epoxy propane copolymer, the acrylate of end capped oxyethane of alkyl oxide list and epoxy propane copolymer, the acrylate of the methacrylic ester of end capped oxyethane of alkyl ester list and epoxy propane copolymer or end capped oxyethane of alkyl ester list and epoxy propane copolymer; The mass content of cationic polymers part is 25%～75% in the cation polymer hydrogel sub-micrometer grain, cationic monomer is selected from methacrylic acid-N, N dimethylamine base ethyl ester, vinylformic acid-N, N dimethylamine base ethyl ester, methacrylic acid-N, N dimethylamine base ethyl ester, vinylformic acid-N, N dimethylamine base ethyl ester, methylacryoyloxyethyl dimethyl octyl group brometo de amonio, acrylyl oxy-ethyl dimethyl octyl group brometo de amonio, methacrylic acid ester quat, quaternary ammonium acrylate, Methacrylamide quaternary ammonium salt or acrylamide quaternary ammonium salt; The mass content of initiator is 0.7%～3% in the cation polymer hydrogel sub-micrometer grain, and initiator is selected from Diisopropyl azodicarboxylate, 2,2'-Azobis(2,4-dimethylvaleronitrile), dibenzoyl peroxide or di-isopropyl peroxydicarbonate; The mass content of linking agent is 0.7%～3% in the cation polymer hydrogel sub-micrometer grain, and linking agent is selected from TEG-double methyl methacrylate, N,N methylene bis acrylamide or Vinylstyrene.
2. cation polymer hydrogel sub-micrometer grain method for preparing described redispersible of claim 1 and pH susceptibility, it is characterized in that, with non-ionic water-soluble macromonomer and cationic monomer, linking agent and initiator, pressing mass ratio 20%～70%:25%～75%:0.7%～3%:0.7%～3% adds in the reactor, be dissolved in acetonitrile or the ethanol, logical nitrogen 20min, 80 ℃ of back flow reaction 6h, air distillation goes out acetonitrile or alcoholic acid drips redistilled water simultaneously, the distillation finish after with the dispersion liquid naturally cooling, with the refrigerative dispersion liquid behind centrifugal 15min under the 3000rpm, with the supernatant liquid intercepting relative molecular mass of packing into is the 72h that dialyses in 8000-14400 the dialysis tubing, and the dispersion liquid after the dialysis gets the white powder product through lyophilize.
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| CN101265312B (en) * | 2008-05-07 | 2010-07-21 | 天津大学 | Amphipathic three block copolymer and its preparation method and application |
| CN103962111B (en) * | 2014-05-08 | 2016-02-17 | 闽江学院 | Cationic water gel rubber material |
| CN107759725B (en) * | 2017-11-10 | 2020-02-18 | 中国石油大学(华东) | PH-sensitive water-absorbent resin suitable for oil well cement slurry and application thereof |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4060678A (en) * | 1975-02-11 | 1977-11-29 | Plastomedical Sciences, Inc. | Cationic hydrogels based on hydroxyalkyl acrylates and methacrylates |
| CN1072843A (en) * | 1991-10-16 | 1993-06-09 | 理查森-维克斯有限公司 | Gel-type cosmetic composite |
| US6039940A (en) * | 1996-10-28 | 2000-03-21 | Ballard Medical Products | Inherently antimicrobial quaternary amine hydrogel wound dressings |
| CN1594384A (en) * | 2004-06-18 | 2005-03-16 | 武汉大学 | Biodegradable temperature-sensitive hydrogel and method for preparing same |
-
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- 2006-12-21 CN CNB2006101305021A patent/CN100463930C/en not_active Expired - Fee Related
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4060678A (en) * | 1975-02-11 | 1977-11-29 | Plastomedical Sciences, Inc. | Cationic hydrogels based on hydroxyalkyl acrylates and methacrylates |
| CN1072843A (en) * | 1991-10-16 | 1993-06-09 | 理查森-维克斯有限公司 | Gel-type cosmetic composite |
| US6039940A (en) * | 1996-10-28 | 2000-03-21 | Ballard Medical Products | Inherently antimicrobial quaternary amine hydrogel wound dressings |
| CN1594384A (en) * | 2004-06-18 | 2005-03-16 | 武汉大学 | Biodegradable temperature-sensitive hydrogel and method for preparing same |
Non-Patent Citations (2)
| Title |
|---|
| pH敏感性水凝胶的制备与作用原理. 肖君等.河南化工，第8期. 2003 |
| pH敏感性水凝胶的制备与作用原理. 肖君等.河南化工，第8期. 2003 * |
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Assignee: TIANJIN DEVELOPMENT KETAI CHEMICAL NEW MATERIAL DEVELOPMENT Co.,Ltd. Assignor: Tianjin University Contract fulfillment period: 2009.9.25 to 2014.9.24 Contract record no.: 2009120000227 Denomination of invention: Redispersable pH-sensitive cation polymer hydrogel sub-micrometer grain and its preparation method Granted publication date: 20090225 License type: Exclusive license Record date: 20090925 |
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