Tadpoles from the Intramolecular Photo-Cross-Linking of Diblock Copolymers

Abstract

Preparation of tadpoles or globule−coil diblock copolymers from three coil−coil diblock copolymers is reported. The coil−coil copolymers consist of one poly(tert-butyl acrylate)-block-poly(2-cinnamoyloxyethyl methacrylate) or PtBA-b-PCEMA sample and two PtBA-b-P(CEMA-ran-hCEMA) samples. Here P(CEMA-ran-hCEMA) denotes poly[(2-cinnamoyloxyethyl methacrylate)-ran-(2-hydrocinnamoyloxyethyl methacrylate)]. The tadpoles are prepared by photo-cross-linking the PCEMA or P(CEMA-ran-hCEMA) blocks intramolecularly. Intramolecular cross-linking competes with intermolecular cross-linking. The former is encouraged by adding a diblock copolymer solution at a low pumping speed into a solvent under constant UV irradiation and stirring. The irradiation ensures that the newly added copolymer is immediately converted into tadpoles. The slow copolymer addition ensures that the copolymer concentration in the photoreactor remains low throughout the photolysis process. Factors affecting the purity, yield, and compactness of the tadpoles produced are examined.