Light-scattering study of temperature-responsive poly(acryloyl- l-proline methyl ester)

Abstract

Poly(acryloyl- l-proline methyl ester) (A-ProOMe) obtained by radiation-induced polymerization exhibited a lower critical solution temperature (LCST) at ca 14°C. Physical properties such as molecular weight ( M W ), particle radius of gyration ( 〈S 2〉 1 2 ), and particle size distribution were investigated by static and dynamic light-scattering measurements as a function of temperature. The M W of poly (A-ProOMe), obtained by irradiating up to 30 kGy at 25°C, increased from 1,270,000 at 10°C to 56,100,000 at 20°C in water; on the other hand, the 〈S 2〉 1 2 value decreased with rise in temperature, e.g. from 40.5 to 20.1 nm between 10 and 20°C. From the results of particle size distribution, it was concluded that polymers, dissolved in water below the LCST, aggregate to make globules above LCST.