Synthesis And Study On Self-assembly Of Amphiphilic Random Copolymer

In this paper, the amphiphilic random copolymers poly (styrene-co-acrylic acid) (P(St-co-AA)) were synthesized by atom transfer radical polymerization(ATRP), and the amphiphilic random copolymers P(NIPAM-co-AA-co-CEA) were synthesized by free-radical solution polymerization. Self-assembly of P(St-co-AA) and P(NIPAM-co-AA-co-CEA) were respectively researched.A series of random copolymers poly(styrene-co-tert-butyl acrylate) (P(St-co-tBA)) with different monomer ratio were synthesized by atom transfer radical polymerization (ATRP), using hydrophobic styrene(St) and tert-butyl acrylate(tBA) as monomers, ethyl-2-bromo- propionate as initiator, compound system of CuCl/ N,N,N′,N′′,N′′- penta-methyl-diethylenetri- amine as catalyst. Amphiphilic random copolymers P(St-co-AA) were obtained from hydrolyzed P(St-co-tBA) copolymers with trifluoroacetic acid as catalyst. P(St-co-tBA) and P(St-co-AA) copolymers were characterized by means of FTIR , 1H NMR, Gel Permeation Chromatography(GPC) and Differential Scanning Calorimetry(DSC). Self-assembly of P(St-co-AA) copolymers in selective solvent was characterized by means of UV, laser light scattering(LLS), laser granularity analyzer and TEM. Effect of copolymer composition, polymer concentration and water content on self-assembly were discussed.The random copolymer P(St-co-AA) was synthesized by radical solution polymerization and atom transfer radical polymerization(ATRP). The mechanism of different polymerization was different, so the inner segment sequence was different. As self-assembly was relation with the segment sequence, so effect of polymerization methods on self-assembly was researched primarily.Self-assembly of poly(N-isopropylacrylamide-co-acrylic acid-co- 2-cinnamoylethyl acrylate) [P(NIPAM-co-AA-co-CEA)], which was obtained from the radical solution polymerization was studied. At room temperature, the random copolymers self-assembly into spherical core-shell micelles with hydrophobic PCEA segment as the core, hydrophilic PNIPAM/PAA segments as the mixed shell. Increasing temperature, the diameters of micelles were reduced because of collapsed PNIPAM with PCEA as the core. Decreasing pH, PAA chains collapsed onto the core resulting in reducing of the diameters of micelles. Moreover, by UV light, the diameters of micelles reduced because of photo-crosslinking of the PCEA segment as the core.As the micelles were amphiphilic, which were similar to surfactant. Using micelles of P(NIPAM-co-AA-co-CEA) as emulisifer was studied, and effect of temperature, UV irradiation and pH were researched.