4-Acetoxystyrene-styrene copolymers

Block copolymers with hydroxyl segments were prepared by various ways An example utilizes the copper-catalyzed sequential copolymerizations of nBA and 2-[(trimethylsilyl)oxy]ethyl acrylate by the macroinitiator method into B-31 to B-33. The copolymers were then hydrolyzed into amphiphilic forms by deprotection of the silyl groups.313 A direct chain-extension reaction of polystyrene and PMMA with HEMA also afforded similar block copolymers with hydroxyl segments (B-34 and B-35).241-243 In block polymer B-36, a hydroxy-functionalized acrylamide provides a hydrophilic segment.117 Block copolymers of styrene and p-acetoxystyrene (B-37 to B-39), prepared by iron... 

For styrene-based random copolymers, functional groups can be introduced into the polymer chains via copolymerization with functional styrene derivatives, because the electronic effects of the substituents are small in the metal-catalyzed polymerizations in comparison to the ionic counterparts. Random copolymer R-6 is of this category, synthesized from styrene and />acetoxystyrene.372 It can be transformed into styrene// -vinylphenol copolymers by hydrolysis.380 The benzyl acetate and the benzyl ether groups randomly distributed in R-7 and R-8 were transformed into benzyl bromide, which can initiate the controlled radical polymerizations of styrene in the presence of copper catalysts to give graft copolymers.209 Epoxy groups can be introduced, as in R-9, by the copper-catalyzed copolymerizations without loss of epoxy functions, while the nitroxide-mediated systems suffer from side reactions due to the high-temperature reaction.317... 

There have been several other well-defined random copolymers based on styrene derivatives prepared with trimethylsilylstyrene [123], p-acetoxystyrene [124], p-methoxymethylstyrene, and p-acetoxymethylstyrene [125]. The resulting copolymers served as precursors to functional materials with Si, phenol, or hydroxybenzyl moieties, or for subsequent crosslinking or grafting processes. 

Kuo, S. W., and Chang, R C. 2001. Effect of copolymer composition on the miscibility of poly(styrene-co-acetoxystyrene) with phenolic resin. Polymer 42 9843-9848. 

A cationic to ATRP transformation was also used in the synthesis of triblock copolymers with polyisobutylene (PIB) as the middle sequence. These materials are particularly useful as thermoplastic elastomers. In this case, a few units of styrene were added to living difunctional PIB after the isobutylene had reacted. The isolated PIBs could act as bifunctional macroinitiators for ATRP [86]. A similar strategy was used by Batsberg et al. [87] for the synthesis of block copolymers of isobutylene with p-acetoxystyrene (PlB-fo-PAcSt) or styrene (PlB-b-PSt). 

NMRP has been used for the preparation of diblock copolymers of St, other styrenic derivatives, and various different monomers such as PAcOSt-l -PSt (AcOSt 4-acetoxystyrene), PVBCl-li-PSt (VBCl vinylbenzylchloride), PBA-b-PSt, PSi-b-P2VP, PMMA-li-PSt, and rod-coil block copolymers consisting of p-acetoxystyrene as the coil segment and... 

A similar synthetic procedure was used to prepare the various random copolymers of (a) 4-acetoxystyrene and styrene or (b) styrene and t-butyl acrylate. Deacetylation of Poly(4-acetoxystyrene-co-styrene) (5). To a slurry of poly(4-acetoxystyrene-co-styrene) (70 30) (2) (10.0 g, 0.069 mol) in methanol at reflux (50 mL), under N2, ammonium hydroxide (5.33 g, 0.152 mol) dissolved in water (10 mL) was added dropwise over 15 minutes. After addition, the reaction mixture was heated at reflux for 18 hours, during which time the polymer went into solution. The reaction is then cooled to room temperature, and the polymer isolated by precipitation into water (500 mL), filtered, washed well with water, and dried in a vacuiun oven overnight at 50°C. Isolated yield of poly(4-hydroxystyrene-co-styrene) (6) 85% of theory. M = 7278, = 8297, PD = 1.14. 

These short TEMPO capped styrene blocks (7) were then used as "macroinitiators for the further polymerization of 4-acetoxystrene (1) using the same procedure as described above. The length of the acetoxystyrene block is controlled by the ratio of the "macroinitiator (7) to acetoxystyrene monomer. The acetoxystyrene block was then converted to 4-hydroxystyrene by quantitative base hydrolysis of the acetoxy groups as previously described. Table 1. A similar synthetic strategy was used for the preparation of poly(styrene- co-t-butyl acrylate) block copolymers. 

Poly(4-acetoxystyrene) with = 10000, PDI =1.12 was prepared by bulk RAFT polymerization of 4-acetoxystyrene at 90 °C using AIBN as initiator and a-acetic acid dithiobenzoate as chain transfer agent, and used as a macrotransfer agent in the block copolymerization of St with AIBN initiator after reprecipitation and the removal of residual monomer. The block copolymer, RB-2 was obtained [46]. The block copolymer can be hydrolyzed under mild basic conditions to give poly(4-hydroxy styrene)- )-PSt [46]. 

Hodges et al. [152] and Bian and Cunningham [153] reported the grafting of PS, poly(acetoxystyrene), poly[styrene-b-(methyl methacrylate-co-styrene)], poly(acetoxystyrene-co-styrene), and poly(styrene-co-2-HEMA) copolymers onto 2,2,6,6-tetramethyl-l-piperidinyloxy nitroxide (TEMPO) bound Merrilield resin. Merrifield resin is a PS resin based on a copolymer of styrene and chloromethylstyrene cross-linked with divinylbenzene. In these works, a pronounced increase of particle size was observed, which was attributed to the formation of chains both at the surface and within the microspheres. The polymerization control was enhanced both on the surface and in solution by the addition of sacrificial nitroxide. 

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