Polyether-Based Diblock Copolymers

Poly(ethylene glycol)-polypeptide block copolymers are of particular interest, from both a structural and a functional point of view. In addition to microphase separation and the tendency of the peptide blocks towards aggregation, crystallization of poly(ethylene glycol) (PEG) introduces an additional factor that can influence the structure formation of these hybrid block copolymers. Ma and coworkers (Zhang et ai, 2003) have investigated the solid-state structure and properties of three poly(ethylene glycol)-Z /ocA -poly(L-Alanine) (PEG-Z -PLAla) copolymers that were prepared from a PEG macroinitiator with M = 2 kg/mol. The diblock copolymers contained 39.8, 49.6 and 65.5 mol% alanine. Erom FTIR spectra and differential scanning calorimetry (DSC) measurements, the authors proposed a microphase-separated bulk structure. 

AB diblock and ABA triblock copolymers composed of PEG as the A block and random coil segments of poly(D,L-valine-co-D,L-leucine) as the B block(s) were investigated by Cho and coworkers (Cho et al, 2003). DSC experiments revealed PEG crystallization and showed that 

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