Synthesis of Poly[ethylene-co-(vinyl acetate)-g-(2-alkyl-2-oxazoline)]s

Abstract

ABSTRACT:For preparation of a graft copolymer having a polyethylene main chain and poly(N-acylethylenimine) graft chain, poly[ ethylene-co-(vinylacetate )-g-(2-alkyl-2-oxazoline )]s ( 4) were prepared. First, poly[ethylene-co-(vinyl acetate)] (1) was saponified to give polymer (2) having a hydroxy group. Secondly, 2 was tosylated or bromoacetylated giving rise to polymer (3a) or (3b). Then, polymer 3 was employed to initiate the cationic ring-opening polymerization of 2-methyl-2-oxazoline or 2-ethyl-2-oxazoline to produce a graft copolymer which was isolated by reprecipitation. During the graft copolymerization, a homopolymer of 2-oxazoline was produced probably due to chain-transfer, the highest graft-efficiency being 50%. KEY WORDSPoly(2-oxazoline) Graft Copolymer / Poly[ethyl-co-vinyl acetate)] / Vinyl Alcohol Unit / Tosylation / Bromoacetylation / Polymerization chemistry of 2-oxazolines and other cyclic imino ether monomers has greatly developed for these two decades. The cationic ring-opening polymerization of 2-alkyl-2-oxazolines produces poly(N-acylethylenimine )s and their hydrolysis gives linear polyethylenimine. 1 Through our recent studies on the polymerization of 2-oxazolines 2 we observed the following characteristic features; i) polymerization can be initiated by alkyl sulfonates or alkyl halides, ii) propagation is of a highly living nature, and iii) the product poly(N-acylethylenimine) is hydrophilic or lipophilic depending upon the nature of the acyl group. Based on these characteristics, various block and graft copolymers of 2-oxazolines have been prepared.1. 2 Several papers have reported graft copolymers from 2-oxazolines: poly[ styrene-g-(2-methyl-2-oxazoline )], 3 .4 poly[butadiene-g-(2-methyl-2-oxat To whom all correspondence should be addressed.zoline)], 5 poly[(vinyl chloride)-g-(2-methyl-2-oxazoline )] 6 poly[(2-phenyl-2-oxazoline )-g-( ethylene oxide)],7 and cellulose diacetate-gpoly(2-alkyl-2-oxazolines), 8 and poly[methyl methacrylate-g-(2-oxazoline)]s. 9 We also prepared graft copolymers having poly(2-oxazoline) segments both in the main and graft chains, which show good surfactant nature reflected by a surface tension (y) value. 10 The present paper describes the synthesis of graft copolymers having poly[ethylene-co-(vinylacetate)] [poly(E-co-V Ac)] main chain and poly(2-alkyl-2-oxazoline) (polyROZO) graft chain, which is an extension study of the synthesis of graft copolymers from 2-oxazolines. 3 -5 • 7 -10 The main purpose of this study is to modify the surface nature of polyethylene by introducing the graft chain of poly(N-acylethylenimine).

Cylindrical Molecular Brushes of Poly(2-oxazoline)s from 2-Isopropenyl-2-oxazoline

“…While 2-methyl-2oxazoline (MeOx) will give very hydrophilic brushes, 2-ethyl-2-oxazoline (EtOx) and 2-isopropyl-2-oxazoline (iPrOx) are converted to monomer units of slight amphiphilicity, and the resulting polymers are known to show a sharp LCST. [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51] As outlined in Scheme 1, we prepared the molecular brush backbone by free radical as well as living anionic polymerization. While the latter gives narrow molar mass distributions and thus a better overall definition of the resulting molecular brushes, the free radical polymerization of IPOx is facile, straightforward, and better suitable for large-scale production.…”

“…45,46 For the grafting-from approach, several synthetic strategies are possible. Kobayashi et al 47 used hydroxyl groups of saponified poly[ethylene-co-(vinyl acetate)] to create pendant tosylate moieties for the grafting of POx side chains, and Nuyken et al [48][49][50][51] used linear as well as (hyper)branched macroinitiators containing benzyl chloride functions for the grafting of 2-oxazolines. Both approaches led to comb polymers with POx side chains of considerable grafting density.…”

“…For the preparation of POx cylindrical molecular brushes all three routes (grafting-from, -through, or -to) are possible; however, e.g., the grafting through of POx macromonomers was employed with comonomers to realize sufficient degrees of polymerization. − Since POx is prepared by LCROP, it is of advantage to use the grafting-from approach, analogue to the surface-initiated polymerization of 2-oxazolines on surfaces or nanoparticles. , For the grafting-from approach, several synthetic strategies are possible. Kobayashi et al used hydroxyl groups of saponified poly[ethylene- co -(vinyl acetate)] to create pendant tosylate moieties for the grafting of POx side chains, and Nuyken et al − used linear as well as (hyper)branched macroinitiators containing benzyl chloride functions for the grafting of 2-oxazolines. Both approaches led to comb polymers with POx side chains of considerable grafting density.…”

Poly(2-oxazoline) molecular brushes by grafting through of poly(2-oxazoline)methacrylates with aqueous ATRP

“…5,6 Molecular brushes based on poly(2-oxazoline)s (POx) got in focus of recent research because of the advantageous properties of POx as a biomaterial. 7,[21][22][23][24][25][26][27][28][29][30] After early approaches 31,32 yielding a variety of POx-based comb polymers, [33][34][35][36][37][38][39][40][41][42][43][44][45][46] POx molecular brushes have been synthesized recently by several routes. 7,8 Similar to poly(ethylene glycol) (PEG), hydrophilic POx is non-toxic, 9,10 non-immunogenic (low to none complement activation), 10,11 suppresses biofouling, 12,13 POxylated entities display the same "stealth effect" as PEGylated ones, [14][15][16] and hydrophilic as well as amphiphilic POx shows a biodistribution and excretion which is beneficial for medical applications.…”

“…8,[18][19][20] Furthermore, multiple functionalization and structural versatility are possible using respective initiators, monomers and terminating agents. 7,[21][22][23][24][25][26][27][28][29][30] After early approaches 31,32 yielding a variety of POx-based comb polymers, [33][34][35][36][37][38][39][40][41][42][43][44][45][46] POx molecular brushes have been synthesized recently by several routes. The majority of the applied methods focuses on the polymerization of macromonomers by group transfer polymerization(GTP), free radical polymerization (FRP) or reversible addition/fragmentation chain transfer polymerization (RAFT).…”