Hydroxyl-terminated chains, reactive

Polymerization could be terminated by several mechanisms. Cycliza-tion of the growing oligomer terminates chain growth. Reaction of the reactive chain ends with water resulted in the formation of hydroxyl (tetrahydrothiophenium ring termini) and carboxylic acid end groups. 

The aim of this review is to summarize the developments concerning the synthesis of hydroxyl-terminated polymers by a radical process. Hydroxytelechelic , a term also used for denominating this type of polymers, means the presence of one OH group at each end of the macromolecular chain. These reactive ends can be further used for chain extension or network build-up if a multifunctional reagent is used, but these must be distinguished from macromonomers as pointed out by Rempp and Franta 1). 

Block copolymers of lactide with glycolide have been prepared by sequential addition of monomer onto the reactive chain end of polymer produced from another monomer, or by using a hydroxyl-terminated homopolymer as a chain transfer agent [17]. 

Two separate series of experiments were carried out in order to study the reactivity of EPR-g-SA towards low Mw diols with or without the addition of a tertiary amine as catalyst, and the reactivity of EPR-g-SA towards a long-chain hydroxyl-terminated polybutadiene (HTPB). For both of them, the same experimental procedure was followed to ensure an intimate mixing of the reactants, they were all dissolved in a common solvent at room temperature and in a certain stoichiometric amount (in solution, the kinetics of esterification is very slow, thus the degree of reaction is negligible). Subsequently, the solvent is quickly removed by evaporation under vacuum at room temperature directly onto KBr disks to obtain a film which is used for IR analysis. 

The incorporation of saturated segments into molecules of unsaturated polyesters is not limited to poly(oxyethylene) blocks. Apphcation of hydroxyl-terminated segments of perfluoropolyethers represents another approach [71]. In contradistinction to the poly(oxyethylene) segments (Scheme 15) the perfluoropolyethers (Scheme 16) contain two reactive terminal functional groups and thus are randomly incorporated along the chain of unsaturated... 

More specifically, the hydroxyl terminated polymer is polystyrene (PS-OH). This latter can be prepared relatively easily following classical anionic polymerization procedures. The isocyanate moiety involved in the polymer chains is 3-isopropenyl-a, a -dimethylbenzyl isocyanate (TMI), which is randomly distributed along the chain. If the polymer backbone bearing TMI is identical or miscible with PS-OH, the reactive system is homogeneous. 

In another development, the use of diketenes as polymer intermediates that are similar in reactivity to the aromatic diisocyanates has been described. A particularly interesting diketene is anthracene-9,10-diketene, shown in Equation 4. Polymers, polyamides and polyesters, especially those from polyetherglycols and polyesterglycols, have been prepared. These diketenes, as reactive polymer intermediates, are also of potential interest for chain extension reactions on hydroxyl-terminated polyesters. 

Bisphenol A, whose official chemical name is 2,2-bis(4-hydroxyphenyl)propane, is a difunctional monomer with two reactive hydroxyl groups, as shown in Fig. 20,2. It polymerizes svith dicarbonyl organic monomers, such as phosgene or diphenyl carbonate, which are illustrated in Fig. 20.3. During polymerization, shown in Fig. 20.4, the hydroxyl groups of the bisphenol A deprotonate in the presence of a base. After deprotonation, the oxygen atoms on the bisphenol A residue form ester bonds with the dicarbonyl compounds. The polymerization process terminates when a monohydric phenol reacts with the growing chain end. 

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