Hydroxyl group reactions ring-opening polymerization

By using a combination of RAFT and ring opening polymerization (ROP), (polyethylene oxide) methyl ether)(polystyrene)(poly(L-lactide) 3-miktoarm star terpolymers have been successfully synthesized [182]. The synthetic approach involved the reaction of the cw-functionalized - OH group of the poly(ethylene oxide) methyl ether with maleic anhydride under conditions where only one hydroxyl group can be esterified (MPEO). The double bond... 

By utilizing a combination of RAFT and cationic ROP, the synthesis of [poly(methyl methacrylate)][poly(l,3-dioxepane)][polystyrene] miktoarm star terpolymers was achieved [182], The approach involved the synthesis of PS functionalized with a dithiobenzoate group by RAFT polymerization and subsequent reaction with hydroxyethylene cinnamate (Scheme 98). The newly created hydroxyl group was then used for the cationic ring opening polymerization of 1,3-dioxepane (DOP). The remaining dithiobenzoate group was used for the RAFT polymerization of methyl methacrylate. 

Many of the common condensation polymers are listed in Table 1-1. In all instances the polymerization reactions shown are those proceeding by the step polymerization mechanism. This chapter will consider the characteristics of step polymerization in detail. The synthesis of condensation polymers by ring-opening polymerization will be subsequently treated in Chap. 7. A number of different chemical reactions may be used to synthesize polymeric materials by step polymerization. These include esterification, amidation, the formation of urethanes, aromatic substitution, and others. Polymerization usually proceeds by the reactions between two different functional groups, for example, hydroxyl and carboxyl groups, or isocyanate and hydroxyl groups. 

For selectiveness of initiation of graft reactions, the use of a tin octoate (SnOct2) (or tin(II) 2-ethylhexanoate) catalyst is convenient for preparing this type of copolymers, polysaccharide-gra/f-PHAs, because the ring-opening polymerization of cyclic esters such as lactides and e-caprolactone (CL) can be initiated efficiently by hydroxo-initiators (i.e. based on hydroxyl groups) in the presence of SnOct2 [12-16], as exemplified in Scheme la. 

The melt condensation of acid and hydroxyl functional group normally requires exact stoichiometry, elevated temperature, and a long reaction cycle. Such a route would not be possible to utilize to produce block polymers from lactones and other vinyl monomers. However, a rather facile route leading to polyester formation can be realized by the ring-opening polymerization of lactones as seen from the scheme ... 

The absence of linear oligomers is due to rapid reactions of the hydroxyl and oxonium ion end groups. This mechanism is quite general [67, 68] for ring-opening polymerizations of cyclic ethers initiated with string protonic acids. Substituted tetrahydrofurans generally resist polymerizations. 

In the typical ring-opening polymerization, reactive hydroxyl groups are automatically formed at the ends of the chains. " Substitution reactions... 

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