Synthesis, graft copolymer groups

Hydroxyl and carboxyl functional groups are very valuable in the chemistry of polymers due to the wide variety of reactions that can be carried out through these intermediates, such as transformations into other useful functional groups or block and graft copolymer synthesis. Thus, there have been many attempts to synthesize PIBs with such end groups, mostly by rather cumbersome methods Most of these... 

By living cationic polymerization, our group has investigated the synthesis of polymers of various shapes including gradient copolymers,PVA graft copolymers,and end-functional polymers for the modification of liposomes to provide controlled release of drugs. 

Shibi IG, Anirudhan TS. Synthesis, characterization, and application as a mercury (II) sorbent of banana stalk (Musa paradisiaca)-polyacrylamide grafted copolymer bearing carboxyl groups. IndEng Chem Res 2002 41 5341-5352. 

Considerable progress has been made in the synthesis of tailor-made block copolymers, and to some extend also to the corresponding graft copolymers, by living ionic polymerization, controlled free-radical polymerization and quite recently by non-covalent coupling techniques. Numerous examples of linear water-soluble A-B and A-B-A structures were described in addition to the possibility of functionalization of these copolymers with specific groups, such as reactive double bonds, ionic groups, fluorescence labels, either at the chain ends and/or at the junction of the blocks. 

The reactions of the enolates of aldehydes and ketones with copper (II) salts have been known for many years to yield a-acylcarbon-centered radicals which couple to form 1,4-dicarbonyl compounds in nearly quantitative yields (i-J).We have found that the radicals that are intermediates in these reactions are useful for initiating polymerization reactions and have shown that these reactions are very valuable for the synthesis of polymers with useful end-group functionality, block copolymers and graft copolymers 4-8). 

Macromonomer method Macromonomers are conveniently used for the graft copolymer synthesis. A macromonomer of PEG chain having an oxazoline polymerizable group was prepared and used for a graft copolymer synthesis (Scheme 23). ... 

Otsu et al. [48] have also reported a solid-phase block copolymer synthesis using a PSt-gel photoiniferter that is, the Et2NCSS- group attached to PSt-gel through a hydrolizable ester spacer was prepared and used as a photoiniferter of the polymerization of St. The resulting grafted PSt onto PSt-gel acted as a macroiniferter for radical polymerization of MMA. In this way, a homopolymer of MMA was easily separated from the graft-block copolymer attached to PSt-gel. Hydrolysis of the latter yielded a... 

Gross-Linking. A variety of PE resins, after their synthesis, can be modified by cross-linking with peroxides, hydrolysis of silane-grafted polymers, ionic bonding of chain carboxyl groups (ionomers), chlorination, graft copolymerization, hydrolysis of vinyl acetate copolymers, and other reactions. 

Group-Transfer Polymerization. Living polymerization of acrylic monomers has been carried out using ketene silyl acetals as initiators. This chemistry can be used to make random, block, or graft copolymers of polar monomers. The following scheme demonstrates the synthesis of a methyl methacrylate—lauryl methacrylate (MMA—LMA) AB block copolymer (38). LMA is CH2=C(CH2)COO(CH2) CH2. 

Qiu et al. [241 have reported the synthesis of macromolecules having 4-tolylureido pendant groups, such as poly(N-acryloyl-N -4-tolylurea-cvi ethyl acrylate) [po-ly(ATU-co-EA)] 18, and poly(N-methacryloyl-A/ -4-tol-ylurea-co-EA) [poly(MTU-co-EA)] 19, from the copolymerization of ATU and MTU with EA, respectively. Graft copolymerization of acrylamide onto the surface of these two copolymer films took place using the Ce(lV) ion as initiator. The graft copolymerization is proposed as Scheme (12). 

There are additional factors that may reduce functionality which are specific to the various polymerization processes and the particular chemistries used for end group transformation. These are mentioned in the following sections. This section also details methods for removing dormant chain ends from polymers formed by NMP, ATRP and RAFT. This is sometimes necessary since the dormant chain-end often constitutes a weak link that can lead to impaired thermal or photochemical stability (Sections 8.2.1 and 8.2.2). Block copolymers, which may be considered as a form of end-functional polymer, and the use of end-functional polymers in the synthesis of block copolymers are considered in Section 9.8. The use of end functional polymers in forming star and graft polymers is dealt with in Sections 9.9.2 and 9.10.3 respectively. 

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