Characterization of α, ω-dihydroxypolystyrene by gradient polymer elution chromatography and two-dimensional liquid chromatography

Gradient polymer elution chromatography (GPEC) and GPEC x size-exclusion chromatography (SEC) two-dimensional liquid chromatography (2D-LC) techniques were employed to characterize functionality of hydroxy-telechelic polystyrene (polySt) prepared by two different methods. The first method involved the synthesis of hydroxy-functionalized polySt via atom transfer radical polymerization (ATRP) using a hydroxy-containing initiator and subsequent atom transfer radical coupling (ATRC). For the second method, alpha,omega-dibromo-polySt was synthesized by ATRP using a dibromo-containing initiator, followed by nucleophilic substitution with azide and click reactions. Utilizing GPEC analysis, the polymers were separated according to their hydroxy functionality. The polySt chains containing less hydroxy groups eluted faster. GPEC analysis successfully separated dihydroxy-polySt from monohydroxy- and nonhydroxy-polySt. For the hydroxy-telechelic polySt obtained from ATRC, GPEC analysis provided quantitative information of the termination by coupling during ATRP and the efficiency of ATRC. During the post-polymerization modification of bromo-telechelic polySt by nucleophilic substitution and click reactions, the chain-end functionality of the polySt was changed, while the molecular weight of the polymer remained constant. The powerful ability of GPEC was further demonstrated by sufficiently separating polymers with similar molecular weight but different hydroxy functionality.