Preparation And Properties Of Polylactic Acid Microspheres Via The Combination Of Thiol–ene Click Polymerization And Dispersion Polymerization

The polylactic acid microsphere(PLA microsphere)has received extensive research and attention in the field of drug delivery because of its good biocompatibility and biodegradability.It is difficult to be widely used for ring-opening polymerization of lactides because of its complicated process and high cost.And the polylactic acid microspheres prepared by the traditional emulsion solvent evaporation method are difficult to be widely used because of its many holes and obvious shortcoming.In this paper,low molecular weight PLA prepolymer was prepared by direct condensation polymerization,and microspheres were prepared by using the technique of clicking chemistry and dispersion polymerization.This method is simple,low cost,and has good dispersion of microspheres.This method is expected to be widely used in industry.The star PLA of polyols as nuclear was synthesized by means of direct polycondensation,and star PLA acrylate was prepared by acryloyl chloride sealing end,and the structure of synthetic resin was characterized,thermal performance of synthetic resin was test.PLA microsphere were prepared by step-growth“click”polymerization of star PLA acrylate and PETMP.The effects of polyol structure,content and dispersion polymerization on microsphere morphology,particle size and distribution were studied systematically,and the thermal and degradable properties of microspheres were finally tested.The details are as follows:(1)The three arm star poly(lactic acid)(GPLA)was prepared by direct polycondensation method,and GPLA reacts with acryloyl chloride was prepared three arm star acrylate(GPLAA).The structure of GPLA and GPLAA was characterized by Fourier infrared absorption spectrum(FTIR),nuclear magnetic resonance hydrogen spectrum(~1H-NMR),nuclear magnetic resonance spectra of hydrogen to show that successful with GPLA acryloyl chloride resin reaction,and sealing and rate of99.3%,the molecular weight of the resin was measured by gel permeation chromatography(GPC)and the glass transition temperature of the resin was measured by differential scanning calorimetry(DSC).The microspheres were prepared by click Michael addition reaction under the method of dispersed polymerization.The effects of different stabilizer PVP-K30 dosage,catalyst dosage and mechanical stirring rate on the particle size of microspheres were studied.The microsphere surface morphology was tested by using field emission scanning electron microscope(FE-SEM),and the particle size and distribution of microspheres were calculated by software image-pro Plus6.0.The polymerization process of GPLAA with 5wt%glycerol contentwas studied.As the dosage of stabilizer increased from 1wt%to 3wt%,the particle size of the microspheres decreased from 21.4?m to 7.1?m.As the mechanical mixing rate increased from400rad/min to 1200rad/min,the particle diameter of the microsphere decreased from7.4?m to 3.9?m.With the increase of the catalytic dose from 1wt%to 10wt%,the particle size of the microspheres decreased from 13.4?m to 6.7?m.Finally,the degradation performance of microspheres in artificial gastric juice and PBS buffer was studied.The product of the different contents of glycerol GPLAA step-growth“click”polymerization in the artificial gastric juice degradation rate is faster than in the PBS buffer.and the less glycerin content GPLLA,the better the degradation performance of the product of GPLAA step-growth“click”polymerization,with the increase of glycerol content in GPLAA resin,synthetic product degradation in the artificial gastric juice weightlessness rate reduced from 36.5%to 25%,degradation in PBS buffer weightlessness rate reduced to 16%from 27%.(2)The four arm star poly(lactic acid)(PEPLA)was prepared by direct polycondensation method,and PEPLA reacts with acryloyl chloride was prepared three arm star acrylate(PEPLAA).The structure of PEPLA and PEPLAA was characterized by Fourier infrared absorption spectrum(FTIR),nuclear magnetic resonance hydrogen spectrum(~1H-NMR),nuclear magnetic resonance spectra of hydrogen to show that successful with PEPLA acryloyl chloride resin reaction,and sealing and rate of 99.3%,the molecular weight of the resin was measured by gel permeation chromatography(GPC)and the glass transition temperature of the resin was measured by differential scanning calorimetry(DSC).The microspheres were prepared by click Michael addition reaction under the method of dispersed polymerization.The effects of different stabilizer PVP-K30 dosage,catalyst dosage and mechanical stirring rate on the particle size of microspheres were studied.The microsphere surface morphology was tested by using field emission scanning electron microscope(FE-SEM),and the particle size and distribution of microspheres were calculated by software image-pro Plus6.0.Finally,the degradation performance of microspheres in artificial gastric juice and PBS buffer was studied.The product of the different contents of glycerol PEPLAA step-growth“click”polymerization in the artificial gastric juice degradation rate is faster than in the PBS buffer.and the less glycerin content PEPLLA,the better the degradation performance of the product of PEPLAA step-growth“click”polymerization,with the increase of glycerol content in PEPLAA resin,synthetic product degradation in the artificial gastric juice weightlessness rate reduced from 40.3%to 22.3%,degradation in PBS buffer weightlessness rate reduced to 35.6%from 19.8%.