Characterization of Polystyrene-block-Poly(2-vinyl pyridine) Copolymers and Blends of Their Homopolymers by Liquid Chromatography at Critical Conditions

Abstract

Amphiphilic block copolymers containing poly­(2-vinyl pyridine) (P2VP) as a hydrophilic part and polystyrene (PS) as a hydrophobic segment have a number of applications in modern technology. The presence of a lone pair of electrons on the pyridine moiety of P2VP is exploited for many important applications which on the other hand creates problems in molecular characterization of these polymers by chromatographic methods. P2VP is particularly considered as a unique case for liquid chromatography because of the presence of different types of unwanted polar interactions with most of the stationary phases. Hence, the scientific reports on liquid chromatographic analysis of P2VP homo- and copolymers are scarce. The current study is dedicated to develop a chromatographic characterization method for P2VP-containing copolymers. The major challenge in this context was to develop a system that allows systematic switching of elution behavior of P2VP as a function of mobile phase composition. Chromatographic critical conditions of P2VP are established for the first time on a NP column. The adequacy of the developed method is validated by analyses of blends and block copolymers of P2VP with PS and poly­(methyl methacrylate). Further, chromatographic critical conditions of PS are established on a reversed phase column to evaluate block length of the P2VP block of PS-b-P2VP. The proposed method successfully demonstrates its capability to separate both types of homopolymers from block copolymers alongside estimation of block length of the noncritical segment.

Novel epoxy-terminated macromonomers and their polymerization for synthesis of bottle-brush type amphiphilic block copolymers

“…Liquid chromatography at critical conditions (LCCC) is literally the only technique that can reveal this important information. 36,42–51 The approach requires establishment of chromatographic critical point (CCP) of each block that allows exclusion of the non-critical block. 52–54…”

“…In the ACN/THF MP, 1% of triethylamine (TEA) is added in order to avoid unwanted polar interactions of the polar groups in the polymer chains with free silanol groups of the stationary phase (SP). 46 The eluotropic strength of THF is higher on RP columns compared to ACN. In a MP composition of ACN/THF/TEA: 75/25/01 (V%), PCL eluted in order of decreasing molar mass, a typical SEC regime ( Fig.…”

“…Liquid chromatography at critical conditions (LCCC) is literally the only technique that can reveal this important information. 36,[42][43][44][45][46][47][48][49][50][51] The approach requires establishment of chromatographic critical point (CCP) of each block that allows exclusion of the noncritical block. [52][53][54] In this context, CCP of PCL is established on a RP ODS column in a mobile phase (MP) constituting ACN and THF.…”

Liquid chromatography at critical conditions (LCCC): Capabilities and limitations for polymer analysis

“…He also demonstrated the effect of end groups on linear chains and dangling groups on the cycles by comparing RI and UV traces. Thus the literature on LCCC to separate systems as close as linear and cyclic counterparts remains controversial, unlike in the case of block copolymers where LCCC has proven to be highly productive [17,18].…”

Recent Advances in Separation-Based Techniques for Synthetic Polymer Characterization

“…On the other hand, there were several experimental parameters including column pore size, temperature, solvent composition, and gradients that were important to improve resolution of the noncritical segment in IC (LCCC-IC). In another example, PS- b -poly­(2-vinylpyridine) (PS- b -P2VP) block copolymers were characterized by LCCC under critical conditions for the P2VP block on a normal phase (NP) silica column allowing for characterization of the block length distribution of the noncritical PS block . On the other hand, critical conditions for PS were identified on an RP column, enabling estimation of the block length distribution of the P2VP block.…”