Pendant hydrophilic functional groups

Synthesis of Biodegradable Copolymers with Pendant Hydrophilic Functional Groups... 

With a patented [1], proprietary surface modification, rubber particles are rendered compatible with polyurethanes. One surface modification is a controlled oxidation of the outermost molecules on each rubber particle. The treatment chemistry involves the reaction of halogen- and oxygen-containing gases with the rubber backbone to form pendant polar functional groups. Figure 1. In fact, the rubber surface becomes so hydrophilic that the treated particles are readily wetted by water. 

By the use of the polymer-linking method with 20a, a variety of starshaped poly(vinyl ethers) have been synthesized (Scheme 12) [208-212]. A focus of these syntheses is to introduce polar functional groups, such as hydroxyl and carboxyl, into the multiarmed architectures. These functionalized star polymers include star block (23a,23b) [209,210], heteroarm (24) [211], and core-functionalized (25) [212] star polymers. Scheme 12 also shows the route for the amphiphilic star block polymers (23b) where each arm consists of an AB-block copolymer of 1BVE and HOVE [209] or a vinyl ether with a pendant carboxyl group [210], Thus, this is an expanded version of triarmed and tetraarmed amphiphilic block copolymers obtained by the multifunctional initiation (Section VI.B.2) and the multifunctional termination (Section VI.B.3). Note that, as in the previously discussed cases, the hydrophilic arm segments may be placed either the inner or the outer layers of the arms. 

Hydrophilic or salt forming groups are incorporated into the poljrurethane backbone to make the polymer self-dispersible. These non-reactive poljrurethane dispersions are in aqueous form. Anionic fonns based on pendant acid functional... 

The pendant functions listed in Figure 3 are often useful and of synthetic interest per se. For example, methacrylate and acrylate esters are polymerizable (cross-linking sites) [19-21] the cinnamate is photorespon-sive (for the photo-induced dimerization of its unsaturated groups) [20] oligo(oxyethylene) [25-27] and carbohydrate groups [35] give hydrophilic and water-soluble polymers, whereas perfluoroalkyl moieties [32-34] enhance hydrophobicity. Thus, poly(vinyl ethers) with cinnamate functions... 

Among these, in particular, the acetate [17] and the silyloxyl [31] derivatives are often used as the protecting groups for the hydroxyl (alcohol) function. For example, polymers of 2-acetoxyethyl vinyl ether are readily transformed into a polyalcohol, poly(2-hydroxyethyl vinyl ether), by alkaline hydrolysis [17]. Due to the polar pendant functions, the polymers are of course hydrophilic and often water-soluble, and serve as hydrophilic segments in so-called amphiphilic polymers, as will be discussed later (Sections III.D and VI.B.5). Other important protecting groups include the malonate [23] and the imides [29,30], which lead to polymeric carboxylic acids and amines, respectively (Scheme 1). 

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