Pendent functionalization grafting

Graft copolymer formation may occur by a degradative process through reaction between a pendent functionality on one polymer and main-chain linkages (m the second polymer. Small amounts of cross-linked copolymer may be formed if degradable segments of the graft copolymer read further... 

Fluoropolymers, such as PVDF, PC l FE, and their copolymers, comprise monomer units with pendent secondary fluorine/chlorine atoms, which are potential ATRP initiators. In principle, graft copolymerization initiated from these secondary halides should be possible to allow the preparation of functional graft chains, even though the reaction suffers from low initiation efficiency and requires high reaction temperature. Russell et al. reported the graft copolymerization of St and fm-butyl acrylate (tBA) directly from the secondary chlorine atoms in P(VDF-co-CTFE) via ATRP and illustrated the ability of fluorine atoms to activate the chlorine atoms toward... 

In summary, aliphatic polyesters, already an important class of synthetic degradable polymeric biomaterials, have been taken to unprecedented levels of synthetic diversity and tailoring through the efforts of many research groups in the U.S. and abroad. Some of these have been described in this brief review, with a focus on pendent or graft functionality by polymerization of functionalized lactones, and post-polymerization modification. Future efforts in this area must attempt to connect these synthetic advances to specific applications, through the collaborative efforts of experts in the chemistry, biology, and clinical use of synthetic polymer materials. 

Interfacial polycondensation between a diacid chloride and hexamethylenediamine in the presence of small amounts of ACPC also yield polymeric azoamid, which is a macroazo initiator.[27] In this manner, azodicarbox-ylate-functional polystyrene [28], macroazonitriles from 4,4 -azobis(4-cyano-n-pentanoyl) with diisocyanate of polyalkylene oxide [29], polymeric azo initiators with pendent azo groups [3] and polybutadiene macroazoinitiator [30] are macroazoinitiators that prepare block and graft copolymers. 

Using 4,4,-bis(4-hydroxyphenyl)pentanoic acid (BHPA)196 197 as comonomer, some polysulfones with pendent carboxylic groups were successfully synthesized.198199 Table 6.1 shows the structure of BHPA. The functional groups can be used for the preparation of graft copolymers. 

The same type of graft copolymers with a polystyrene backbone and polypeptide grafts has been synthesized by a different route 89) The monoadduct of DVB and N-ethylethylenediamine was copolymerized with styrene, yielding a random copolymer with pendent primary amine functions. The latter were used as initiators for the subsequent polymerization of the NCA derived from benzyl L-glutamate. 

Graft copolymer formation between two polymers, each with different functionality, may occur either by direct reaction (e.g., A-acid end-group + B-pendent epoxy group), or by addition of a condensing agent that activates functionality of one polymer for reaction with functionality of the second polymer (e.g., A-acid + B-alcohol + triaryl phosphite). 

In theory, it is possible to form block, graft, or crosslinked copolymers by ionic associations. However, in practice, telechelic polymers with ionic functionality at the chain ends are uncommon. Therefore, the majority of reported examples involve crosslinked copolymer formation between two immiscible polymers bearing pendent ionic groups. 

PA/PP blends have been compatibilized through graft copolymer formation between polyamide amine end-groups and pendent anhydride groups on a functionalized polyolefin (Table 5.12). 

PA/PO blends have been compatibihzed through graft copolymer formation between polyamide amine end-groups and pendent anhydride groups on a functionalized styrene copolymer. Also, in one example [Lu et al, 1995] this ternary blend is compatibihzed through copolymer formation between PA and anhydride-functionalized polyolefin (Table 5.14). 

Other Direct Functionalization Reactions. In addition to the above processes, other direct functionalization reactions at the molecular level include the addition of organosilicon hydrides to allyl groups at the terminus of aryloxy side groups (56), the free-radical grafting of epoxy-, organosilyl-, or pyridine-bearing vinyl compounds to p-methylphenoxy side units (57), the quatemization of pendent tertiary amino groups, and... 

The capped radical-generating centers of living polymerization, located on the surface of monolith pores, can be further used for functionalization, by grafting various monomers, for example, vinylbenzyl chloride, tert-butyl methacrylate, or vinylpyridine [393], as well as 2-hydroxyethyl methacrylate and 3-sulfopropyl methacrylate [394]. Another possibiHty for changing the surface chemistry is the involvement of pendent double bonds that remain on the pore surface of highly crossUnked styrene-DVB rods, in a variety of chemical reactions these have been reviewed by Hubbard et al. [395]. 

In the first type of ionic associatitMi (Type 5a), the ionizable functionalities of the two polymers are located in the pendent side groups. These polymers are prepared either through copolymerization with ion-containing monomers (or latent ion-containing monomers) or through subsequent grafting with such... 

PEST/PO blends have been compatibilized through graft copolymer formation by reaction of polyester carboxylic acid end-groups with pendent oxazoline groups on an appropriate PO. The copolymer contains a new esteramide linkage. Womer et al. (1997) have blended 0-20 parts oxazoline-functionalized rubbers containing more than one oxazoline group per chain with 100-80 parts acid-terminated PBT in... 

Sundararaj et al. (1995) have prepared blends containing PP-MA and oxazoline-functionalized PS. A graft copolymer may form through reaction between pendent oxazoUne groups on PS and terminal acid groups (from some hydrolysis of anhydride groups) on PP. Specifically, 80 parts S-lPO (1 % IPO) was blended with 20 parts PP-MA (0.1 % MA) in either an internal mixer at 200 °C or in a TSE. The blends were characterized by selective solvent extraction and SEM. Morphology... 

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