Preparation and Characterization of Cyclic Polystyrenes

Abstract

ABSTRACT:Macrocyclic polystyrenes with various molecular weight were prepared by the reaction of linear polystyrene having two end vinyl groups and potassium naphthalenide as a coupling agent. Intermolecular side reactions produced higher molecular weight polycondensates and undesirable chain termination reactions also produced linear precursors in addition to the designed molecules. In order to isolate cyclic polymers from the ring closure reaction mixtures, preparative size exclusion chromatography (SEC) method was employed. The purity of SEC-fractionated cyclic polystyrenes was rigorously examined by liquid chromatography at the critical condition (LCCC) and interaction chromatography (IC). After SEC-fractionation, we obtained large amount of highly pure cyclic polymers, though high molecular weight cyclic polymers contain very small amount of linear precursor (< 5%). The purity and isotope effect on reversed-phase liquid chromatography (RPLC) were also rigorously investigated by preparing a deuterated cyclic polystyrene. [DOI 10.1295/polymj.37.506] KEY WORDS Cyclic Polystyrene / GPC Fractionation / LCCC / Isotope Effect / Cyclic macromolecules are of great interest in the investigation of the influence of cyclization on their solution, melt, and solid-state properties. Various physical properties of cyclic polymers have been predicted not only by theoretical methods 1-4 but also by computer simulation studies, 5-7 while they have also been examined experimentally. [8][9][10][11][12][13][14] Cyclic polymers were usually synthesized by the coupling reaction between living precursor polymers with functional groups on both ends and bifunctional linking agents. For example, polystyrenes 9,15-19 and poly(2-vinylpyridine)s 20,21 have been synthesized by this method. Furthermore, , !-heterobifunctional polymers have been used for the synthesis of cyclic polymers.22-24 However, side reactions produce linear precursor polymers, and intermolecular reactions simultaneously produce dimeric and higher molecular weight linear polycondensates. Therefore, it is very difficult to obtain pure cyclic polymers directly, and fractionation is necessary in order to obtain cyclic polymers with high purity. For the isolation of cyclic polymers from the ring closure reaction mixtures, two major fractionation methods have been employed: fractional precipitation method 9,14,[16][17][18] and preparative size exclusion chromatography (SEC). 25,26 Furthermore, liquid chromatography at the critical condition method (LCCC) has been successfully applied for the characterization of cyclic polymers.27-30 Throughout these experimental studies, however, the direct evidence of cyclic structure was not shown, in addition to the fact that the purity of the cyclic molecules has not been determined quantitatively in most of the works. Only for the low molecular weight cyclic polymers, the detailed cyclic structures were directly confirmed by NMR analysis of linking points, 22,23 pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), 31 and matri...

Synthesis and characterization of macrocyclic vinyl aromatic polymers

“…A recent report on the electron-transfer-mediated intramolecular coupling of 1,1-diphenylethylene end-functionalized PS seems promising in this regard. 19 DSC measurements indicate that T g 's of the cycles in most cases dramatically differ from those of the matching linear polymers, being largely MW-independent above a DP of about 50. At lower DPs, the T g 's decrease sharply, except for the case of PDMVF, for which apparently the large volume of the 9,9-dimethyl-2-fluorenyl (DMF) pendent groups appears to play a role.…”

Statistical and hydrodynamic properties of topological polymers for various graphs showing enhanced short-range correlation

“…[11,12] Due to novel developments in synthetic chemistry, polymers with different topological structures are synthesized in experiments during the last decade such as not only ring polymers but also tadpole (or lasso) polymers, doublering (or di-cyclic) polymers and even complete bipartite graph polymers. [13,14,15,16,17,18,19,20,21] Lasso polymers are studied also in the dynamics of protein folding. [22] We call polymers with nontrivial topology topological polymers.…”

General Polygonal Length Dependence of the Linking Probability for Ideal Random Polygons

“…18) The contamination of such the linear PSs disturbs clear measurements of A 2 (θ l ) sig-nificantly. Takano et al have recently obtained extremely purified ring PSs with molecular weight M w × 10 −4 = 1.6, 4.17, 10.9 and 57.3 19) and measured A 2 (θ l ) for them. 20) They have applied the liquid chromatography at the critical condition (LCCC) for the fractionation of ring PSs.…”