Copolymers with pendant hydrophilic

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

Hydrophobic regions can be one or two small, well-defined blocks of pendant hydrophobic moieties in an otherwise water-soluble polymer (2-4). An example is a water-soluble sulfonated BAB triblock copolymer where B is hydrophobic f-butylstyrene and A is vinyltoluene (2). However, hydro-phobic regions can also be less well-defined as well as more numerous in a polymer molecule than is the case for a triblock copolymer (5-22). For example, pendant alkyl esters appear to have been randomly incorporated in styrene-maleic anhydride (5) and vinyl benzyl ether-styrene-maleic anhydride (6-ii) copolymers. Also, alkyl polyoxyethylene acrylate monomers can be copolymerized with acrylamide to yield copolymers with pendant hydrophobic chains (12-15). More recently it was found (16-22) that small amounts of water-insoluble monomers that are solubilized by surfactants into aqueous solutions of a hydrophilic monomer produce copolymers with pendant hydrophobic chains, but the size, number, and nature of the hydro-phobic regions has not been determined. 

Methacrylates with pendant oxyethylene units (FM-19) were polymerized in a controlled way with metal catalysts in the bulk or in water. The catalytic systems include a bromide initiator coupled with Ni-2 for n = 2 (bulk, 80 °C)319 and CuCl for n = 7-8.246-320 The latter polymerization proceeded very fast in aqueous media at 20 °C to reach 95% conversion in 30 min and gave very narrow MWDs (MJMn =1.1 — 1.3). The fast reaction is attributed to the formation of a highly active, monomeric copper species com-plexed by the oxyethylene units. A statistical copolymerization of FM-19 (n = 7—8) and FM-20, a methacrylate with a oligo (propylene oxide) pendant group, led to hydrophilic/hydrophobic copolymers with narrow MWDs (MwIMn = 1.2).320... 

The capped allyl polyalkylene oxide can also be based upon propylene oxide or a mixed ethylene oxide-propylene oxide copolymer. The resulting structure is a comb polymer, with pendant capped hydrophilic groups. In aqueous solution, the hydrophilic groups may form a sheath around the hydrophobic silicone backbone to minimize its contact with the water. 

Wahlund et al copolymerized 1-VIA with NIPAAm and employed affinity chromatography to separate the resultant copolymers into two fractions with different physico-chemical characteristics. While copolymers with tmly random distributions of the two monomers did not interact with the metal chelate iminodiacetic acid Sepharose CL 6B (Cfy -ID Asepharose), the other fraction comprising PLCs adsorbed readily. The authors reconciled the observed behavior by the accumulation of the hydrophilic pendant 1-VIA groups responsible for complexing at the hydrophilic periphery of the resultant copolymer. 

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