Controlled Anionic Block Copolymerization with N,N‐Dialkylacrylamide as a Second Block

Abstract

Summary: Novel well‐defined block copolymers composed of polystyrene, poly(2‐vinylpyridine), poly(ethylene oxide), or poly(tert‐butyl methacrylate) as the first block and poly(N,N‐dialkylacrylamide) (PDAlAAm) as the second block were synthesized by ligated anionic polymerization. The latter was carried out in tetrahydrofuran (THF) initiated by 1,1‐diphenyloligostyryllithium in the presence of ZnEt2 and LiCl. At first the role of the additives LiCl and ZnEt2 on the mode of the anionic homopolymerization of N,N‐dialkylacrylamide was investigated. Polymerization in the presence of ZnEt2 resulted in syndiotactic polymers with narrow molecular weight distribution only. In the presence of both additives, the reaction mixture became heterogeneous with a high degree of isotacticity of the polymers. Despite the fact that the polymerizations were performed in heterogeneous phase, the DAlAAm monomers were polymerized in a quantitative yield. The efficiency of the first block of active sites was always higher than 0.71. Preliminary studies using dynamic light scattering of aqueous hydrochloric acid solutions of poly[(2‐vinylpyridine)‐block‐(N,N‐diethylacrylamide)] block copolymers at different temperatures and at pH 2 showed that above 45 °C, micelle‐like aggregates were formed. The heating and cooling cycles were reversible but showed hysteresis, which was obviously due to the isotactic structure of the poly(N,N‐diethylacrylamide) block.Temperature dependence of the scattering intensity of various poly[(2‐vinylpyridine)‐block‐(N,N‐diethylacrylamide)] block copolymers.imageTemperature dependence of the scattering intensity of various poly[(2‐vinylpyridine)‐block‐(N,N‐diethylacrylamide)] block copolymers.

Thermo‐Responsive Ultrafiltration Block Copolymer Membranes Based on Polystyrene‐block‐poly(diethyl acrylamide)

“…[32] By the amount of added Lewis acid and block copolymerization, the solubility of DEAAm can be adjusted. [32,33] In this work, polystyrene-block-poly(diethyl acrylamide) (PSb-PDEAAm) is synthesized with varying chain lengths, and thermo-responsive block copolymer membranes are fabricated using the non-solvent induced phase-inversion process. These membranes are characterized using scanning electron microscopy and water permeation measurements at room temperature and above the LCST.…”

“…[ 32 ] By the amount of added Lewis acid and block copolymerization, the solubility of DEAAm can be adjusted. [ 32,33 ]…”