Synthesis of syndiotactic polystyrene-graft-poly(ethylene glycol) copolymer by photochemical reaction

Syndiotactic polystyrene-graft-poly(ethylene glycol) (sPS-g-PEG) copolymer was prepared by photochemical attachment of poly(ethylene glycol) chains to the benzoylated syndiotactic polystyrene (BesPS) backbone. BesPS, a functional polymer bearing benzophenone moiety, was prepared in a heterogeneous process through Friedel-Crafts acylation reaction using benzoyl chloride as benzoylating agent. This substrate was then dispersed in o-dichlorobenzene at room temperature and mixed with poly(ethylene glycol) , which was reacted with the benzophenone moieties by illumination with UV light (λ > 340 nm). As a result of the photochemical reaction, the hydrophilic poly(ethylene glycol) was chemically attached to the hydrophobic syndiotactic polystyrene backbone. The resultant copolymer was characterized by FT-IR, NMR, and X-ray photoelectron spectroscopy. In addition, the thermal properties of graft copolymers were also studied by means of DSC.