Probing the Effects of Hydrophilic Branch Size, Distribution, and Connectivity in Amphiphilic Polyethylene

Abstract

Acyclic diene metathesis (ADMET) polymerization/hydrogenation methodology was used to synthesize a family of amphiphilic polyethylenes (PEs) with precisely placed poly(ethylene glycol) branches. Four structural parameters are varied in this report: size of the hydrophilic pendant group, manner in which the pendant group is connected to the backbone, distance between the pendant moieties along the backbone, and saturation of the polyolefin backbone. Varying the branch size with other parameters held constant results in negligible effects on thermal behavior. However, when either the distribution of branches or manner of connection of the branches is altered, changes in the thermal behavior become clear. These slight structural changes allow tunability of the structural morphology from fully amorphous to semicrystalline materials melting over a range of temperatures above 60 °C.magnified image

Regioselective Ring-Opening Metathesis Polymerization of 3-Substituted Cyclooctenes with Ether Side Chains.

“…In contrast, the saturated version of polymers showed a glass transition at −79 °C to −57 °C and endothermic peaks at −3.3 °C to −11 °C. Similar behavior is observed for the regularly branched precision LLDPEs, which were synthesized by the ADMET polymerization, reported by Wagener et al − Additionally, a broad exothermic peak was observed between the glass transition and the endothermic peak. We speculate that the broad exothermic peak is attributable to the low-temperature crystallization of polymers, which are in a supercooled state, whereas the endothermic peak is due to melting of the crystallized polymers.…”

Acyclic dienemetathesis: a versatile tool for the construction of defined polymer architectures

“…30a). 111 The results of this study showed that the PEG branches induced folds in the backbone, resulting in small paraffin-like crystallites composed of the methylene sequences between branches (Fig. 30b).…”

“…30 (a) Different ADMET derived polyethylenes containing perfectly spaced hydrophilic PEG branches and (b) chain folding and crystallisation of the ADMET derived amphiphiles. 111 moieties along the backbone, and the saturation of the polyolefin backbone (Fig. 30a).…”

ADMET: Metathesis polycondensation

“…Significant progress has been accomplished in understanding these strictly alkyl functional, and similar effort has been undertaken in more functional PE polymers. As polar group incorporation into a hydrophobic backbone has shown to improve particular properties such as impact resistance and polymer adhesion, but also as chemical barriers, the catalyst developments underlying the ADMET polymerization chemistry here give rise to nearly limitless options with regard to drawing functional groups from the period table ranging from metals67–70 to halogens71–73 and various ether,74–78 ester,79–84 acid,85–87 and ionic88–90 functionality.…”