Monofunctional catalysts monomers

Matyjaszewski et al. showed, however, that when a Cu(I)Br catalyst was used in conjunction with bromine-based initiators for a similar system (St/tBA), the polymerizations were well controlled and chain extension in either direction was possible [194]. This is different from the nitroxide system where chain extension of a pSt macroinitiator with acrylate monomers resulted in low blocking efficiency [71 ]. AB and ABA type block copolymers were prepared using monofunctional and difunctional ptBA or pSt macroinitiators. Deprotection of the ferf-butyl esters in these AB block copolymers afforded amphiphilic block copolymers capable of being used as surfactants for emulsion polymerizations [194,195]. 

Tan et al. explored the synthesis of monomers that are monofunctional. They have synthesized two hypercrosslinked polymer networks of bishy-dro>ymethyl monomers, e.g., 1,4-benzenedimethanol (BDM), and mono-hydro>ymethyl compounds, e.g., benzyl alcohol (BA) by self-condensation. Precursors of polymers like polystyrene and poly(chloromethylstyrene) ° that are swollen, as well as polyfunctional benzyl chlorides, are synthesized by Friedel-Crafts allq lation in the presence of a Lewis acid. Hydroxymethyl and chloromethyl form a bond with the benzene ring in the presence of an acid catalyst,leading to the design of a new series of hypercrosslinked polymers prepared by directly using the building blocks of hydro)g7methyl aromatics (Figure 3.2). 

Porous polymers are prepared by suspension copolymerization of a large excess of monofunctional monomer (e.g. styrene, acrylic acid derivatives or vinylpyrrolidone) with a bifunctional monomer (e.g. divinylbenzene) in a suitable solvent. The cross-linking imparts the required rigidity to the bead polymer structure and, on drying, the solvent evaporates, leaving a porous framework. The choice of reagents, the solvent, catalyst emd the reaction conditions determine bead size and porosity. 

The monomers were generally polymerized in the absence of diluents and catalyst, by heating them above their crystal melting points to produce the corresponding crosslinked liquid crystal homopolymer networks. On occasion a difunctional monomer was mixed with a monofunctional one, such as [131]... 

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