Polymers, functional oxazoline chain ended

Functional Polymers With One 2-oxazoline Chain End and Graft Copolymers Therefrom... 

Functional Polymers with Two 2-oxazoline Chain Ends... 

Surface-initiated living cationic polymerization of 2-oxazolines on planar gold substrates has been reported by Jordan et al (Fig. 9). SAMs of initiators on a planar gold substrate have been used to initiate the living cationic ringopening polymerization of 2-ethyl-2-oxazoline. The polymer chain end was functionalized with an alkyl moiety by means of a termination reaction in order to form an amphiphilic brush-type layer. The resulting layers (thickness... 

Currently, anionic polymerization is regarded as one of the best methods available to prepare end-functionalized polymers. Vinyl polymers with haloalkyl groups at one chain end were prepared by anionic polymerization, followed by termination of the living anion with an excess of 1,2-dichloroethane or 1,4-dibromobutane [102]. These polymers served as macroinitiators for the polymerization of 2-methyl-2-oxazoline (MeOZO) and aromatic vinyl monomers (Scheme 11.27). 

Substituted DPEs have also been utilized to prepare carboxyl-functionalized polymers. The carboxyl functionality has been protected using the oxazoline group. The oxazoline-substituted DPE was not stable to the anionic chain end at room temperature, however. " It was necessary to effect this functionalization reaction in toIuene/THF mixtures (4/1, v/v) at -78 ° C to produce the carboxyl-functionalized polystyrene (Ain = 2.4 X 14.6 X lO gmoh ) in quantitative yield after acid hydrolysis as shown in eqn [42]. Quantitative formation of the oxazolyl-ftmctionalized polystyrene was determined by elemental analysis of the polymer. 

All these a,w-di(oxazoline) oligomers can be useful starting materials for the preparation of regular copolymers, alternating block copolymers, pol3nner networks, or other chain-ended functional polymers. 

Poly(2-oxazoline)s can be prepared by living cationic ring-opening polymerization of the 2-oxazoline monomers utilizing an electrophilic initiator, such as methyl tosylate or methyl triflate. Attack of the monomer onto this initiator leads to the formation of a cationic oxazohnium species and subsequent monomer attack leads to ring-opening while the newly added monomer ends up as a cationic oxazolinium chain end. As such, well-defined polymers can be obtained and the chain-end functionalities can be controlled during initiation and termination (Aoi and Okada, 1996). 

Schemes 64 and 65 outline the synthesis of bifunctional telechelic macromolecules using methylene chloride as a comonomer or chain extender. In the first procedure, the phenolic polymer chain ends are end capped with an electrophilic compound containing a functional group such as p-chloromethylstyrene. The order of the rate constants shown in Scheme 64 is self-explanatory. In the second procedure, the chloromethyl ether chain ends are end capped with a nucleophilic compound containing a functional group such as 2-(p-hydroxyphenyl)-2-oxazoline. " ...

In this way, the functionalization of one component in immiscible polymer blends has attracted great interest in terms of the compatibilization.For example, Lambla and his coworkers reported a series of works on the in situ compatibilization of immiscible polymer blends by one-step reactive extm-sion. ° They described the chemical reactions related to compatibiUzing polymer blends, especially for the PBT/polypropylene (PP) blend system. They stressed that the monomers used for functionalizing PP, such as acrylic acid (ACID), MAH, GMA, and oxazoline, are potentially reactive towards the carboxylic acid and/or hydroxyl groups at the chain ends of the PBT and are melt grafted onto the PP by free-radical reactions. 

Scheme 6.19 Synthesis of chain end-functionalized polymers by terminating the living poly(2-oxazoline) chains with piperazine derivatives.

Poly(2-alkyl oxazoline)s having methacrylate or acrylate end groups were prepared by two methods [182]. a) Living polyoxazoline chains, prepared using methyl p-toluene sulphonate as initiator, were end-capped by reaction with metal salts or tetraalkylammonium salts of acrylic or methacrylic acid or a trialky-lammonium salt or trimethylsilyl ester of methacrylic acid (functional termination). b) The living polymers were terminated with water in the presence of Na2C03 to provide hydroxyl-terminated chains. Subsequent acylation with acry-loyl or methacryloyl chloride in the presence of triethylamine led to the formation of the macromonomers. The procedures are outlined in the following Scheme 51. 

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