Synthesis And PH-sensitive Gelling Behavior Phosphorylcholine Group ABA Triblock Copolymer

When changing external environment, such as pH, temperature, or joining some small molecule and polymer to change the water solubility of the one segment of the block copolymer, environment-sensitive hydrophilic block polymer is self-assembled to obtain different shapes aggregates in an aqueous solution, such as micelles, vesicles, etc. these polymers aggregate has a wide range applications fields for a drug carrier, drug delivery, biologicalmaterials and sewage treatment.The phosphorylcholine motif is an important component of cell membranes, and it is well-known that synthetic phosphorylcholine-based polymers can be used to produce surface coatings that are remarkably resistant to protein adsorption and bacterial/cellular adhesion. Usually, such coatings incorporate phosphorylcholine-containing vinyl monomers such as2-methacryloyloxyethyl phosphorylcholine (MPC). So those biomedical materials are prepared by the MPC for applications in medicine. Biocompatible block polymer micelles and gels have attracted considerable attention because of their potential applications in biomimetic materials, drug delivery materials, biosensors and cosmetics.Biocompatible, pH-responsive ABA triblock copolymers PDEAEMA-b-PMPC-b-PDEAEMA and P(DEAEMA-co-HEMA)-b-PMPC-b-P(DEAEMA-co-HEMA) were prepared by the following three monomers:MPC, DEAEMA and HEM A. We also have studied the properties and micellization behavior of the aqueous solutions of triblock copolymers, and the impact of polyelectrolyte for gelation behavior. Comparing to other reported gelation method, our experimental results show that a physical gel can be obtained at low concentrations by adding the polyelectrolyte, Specific work as follows:1. A series of triblock copolymers PDEAEMA-b-PMPC-b-PDEAEMA and P(DEAEMA-co-HEMA)-b-PMPC-b-P(DEAEMA-co-HEMA) were synthesized using ATRP. The polymer structure, composition and molecular weight were characterized by FT-IR,1H NMR spectra and GPC. pH sensitivity and micellization behavior of the synthesized triblock copolymers aqueous solutions were investigated using UV transmittance measurements, fluorescence probe technique and transmission electron microscopy (TEM). 2. We used three methods to prepare the gels in the alkaline, neutral, acidic conditions by pH-induced, dialysis and adding the polyelectrolyte respectively. Efficiency of pH-induced gelation was proved to be lower, because the formation of free-standing gels need higher concentration of a triblock copolymer solution(10wt%) and higher pH value(pH>9). But in our work, we added polyelectrolyte such as polyacrylic acid (PAA) to the triblock copolymer solution, the results showed that the concentration of the triblock copolymer for gelation was lower than2wt%. Therefore, this method obviously improves the efficiency of the gelation of the polymer. The morphology of the gel was recorded by SEM.