Poly free radical grafting

A radical initiator based on the oxidation adduct of an alkyl-9-BBN (47) has been utilized to produce poly(methylmethacrylate) (48) (Fig. 31) from methylmethacrylate monomer by a living anionic polymerization route that does not require the mediation of a metal catalyst. The relatively broad molecular weight distribution (PDI = (MJM ) 2.5) compared with those in living anionic polymerization cases was attributed to the slow initiation of the polymerization.69 A similar radical polymerization route aided by 47 was utilized in the synthesis of functionalized syndiotactic polystyrene (PS) polymers by the copolymerization of styrene.70 The borane groups in the functionalized syndiotactic polystyrenes were transformed into free-radical initiators for the in situ free-radical graft polymerization to prepare s-PS-g-PMMA graft copolymers. 

Poly( ethylene oxide)-block-poly (propylene oxide)-hZock-poly(ethylene oxide)-g-poly(acrylic acid) (PEO-fc-PPO-fc-PEO-g-PAA, Pluronic-PAA) graft copolymers were synthesized by free radical grafting copolymerization of acrylic acid monomers onto PEO-h-PPO-h-PEO (Pluronic F127) and the aqueous solution properties were characterized by Bromberg [133, 134]. Chiu et al. [135] reported on the micellization of (non-ionic) poly(stearyl methacrylate)-gra/f-poly(ethylene glycol) graft copolymers. 

Acrylic acid and derivatives have been free radically grafted onto the backbone of biodegradable polycaprolactone and poly(lactic-co-glycolic acid). These functionalized biocompatible materials are useful as drug delivery agents. 

Wang used reactive-extrusion polymerization with 2,5-di-methyl-2,5-di-t-bu-tylperoxy hexane to prepared a graft copolymer, (11), by free radically grafting polyethylene-glycol malonic acid onto the biodegradable substrate of poly((3-hydroxybutyrate-co- p-hydroxy valerate). 

Fig, 4, Free radical grafting fi-om azo modified poly(organosiloxane)s... 

From the research of Zhang [88], a novel flax yarn waste-g-poly(acrylic acid-co-acrylamide) [FYW/PAA] superabsorbent composite has been synthesized (Fig. 3.6). In order to develop an eco-friendly superabsorbent composite, flax yarn waste (FYW) was used as raw material. Acrylic acid (AA) and acrylamide (AM) were grafted onto the pretreated flax yarn waste (PFYW) by free-radical graft copolymerization in homogeneous aqueous solution. As a result, the prepared FYW/PAA attained the best water absorbency of 875 g/g in distilled water, 490 g/g in rainwater and 90 g/g in 0.9 wt% NaCl solution. 

The resulting N-radicals, which are all attached to substrate chains, initiate free-radical graft polymerization of suitable vinyl monomers. The method has been applied to synthesize hydrophilic grafts on poly(ether-urethanes)... 

Lao HK, Renard E, ElFagni A, Langlois V, VaUee-Rehel K, Linossier I. Functionalization of Poly(3-hydroxybntyrate-co-3-hydroxyvalerate) Films via surface-initiated atom transfer radical polymerization Comparison with the conventional free-radical grafting procedure. J Appl Polym Sci 2011 120 184—194. 

Polymer Polyols, Free-Radical Grafted Poly(Alkylene Oxide)s... 

A matrix based on guar gum-flfro/t-poly(acrylamide) was developed by microwave-initiated free radical grafting method for controlled release of 5-amino salicylic acid (Fig. 8.2) [21]. The applicability of this matrix for sustained drug release has been investigated by USP drug dissolution method, under different pH environments. 

The structure-property relationship of graft copolymers based on an elastomeric backbone poly(ethyl acry-late)-g-polystyrene was studied by Peiffer and Rabeony [321. The copolymer was prepared by the free radical polymerization technique and, it was found that the improvement in properties depends upon factors such as the number of grafts/chain, graft molecular weight, etc. It was shown that mutually grafted copolymers produce a variety of compatibilized ternary component blends. 

The synthesis of PDMS macromonomers with vinyl silane end-groups and their free-radical copolymerization with vinyl acetate, leading to poly(vinyl acetate)-PDMS graft copolymers, was described 346). The copolymers produced were later hydrolyzed to obtain poly(vinyl alcohol)-PDMS graft copolymers. 

Mixtures of two or more monomers can polymerize to form copolymers. Many copolymers have been developed to combine the best features of each monomer. For example, poly(vinyl chloride) (called a homopolymer because it is made from a single monomers) is brittle. By copolymerizing vinyl chloride with vinyl acetate, a copolymer is obtained that is flexible. Arrangement of the monomer units in a copolymer depends on the rates at which the monomers react with each other. Graft copolymers are formed when a monomer is initiated by free radical sites created on an already-formed polymer chain. 

Virklund, C., Nordstrom, A., Irgum, K. (2001). Preparation of porous poly(styrene-co-divinylbenzene) Monoliths with controlled pore size distributions initiated by stable free radicals and their pore surface functionalization by grafting. Macromolecules 34, 4361-... 

A combination of TEMPO living free radical (LFRP) and anionic polymerization was used for the synthesis of block-graft, block-brush, and graft-block-graft copolymers of styrene and isoprene [201]. The block-graft copolymers were synthesized by preparing a PS-fo-poly(styrene-co-p-chloromethylstyrene) by LFRP [Scheme 110 (1)], and the subsequent re-... 

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