Thermal stimuli‐responsive behavior of pyrene end‐functionalized PDMS through tunable Π–Π interactions. Issue 2 (21st August 2015)

• Record Type: Journal Article
• Authors: Ha, Heonjoo; Shanmuganathan, Kadhiravan; Fei, Yunping; Ellison, Christopher J.
• Is Part Of: Journal of polymer science. Volume 54:Issue 2(2016)
• Page Start: 159
• Page End: 168
• Publication Date: 2015-08-21
• Subjects: stimuli‐responsive -- poly(dimethyl siloxane) -- pyrene; π–π interactions -- graphene oxide; 547
• DOI: 10.1002/polb.23805
• Languages: English
• ISSNs: 0887-6266

Abstract

ABSTRACT: Pyrene end‐functionalized, telechelic poly(dimethyl siloxane) (PDMS) materials were synthesized and their response to different thermal stimuli was evaluated. The incorporation of pyrene end groups introduces strong π–π interactions that facilitated a broad range of thermally responsive properties, in some circumstances forming pyrene nanocrystals that serve as physical crosslinks leading to elastic materials. By synthesizing different chain lengths, samples exhibiting a 7 orders of magnitude change in storage modulus in response to thermal stimuli were produced by modifying only the end‐groups (0.6 wt % of all polymer segments). Repeated thermal cycling during rheological experiments revealed that π–π interaction and crystallization/melting kinetics of pyrene chain‐ends plays a key role in their thermal responsiveness. The properties of these materials were tuned by adding free pyrene, neat PDMS, or graphene oxide (GO) nanoparticles, making them attractive for many applications (e.g., tunable damping materials, heat/light sensors, conductive gels, or light repositionable adhesives). For example, nanocomposites containing 1 wt % GO caused the melting temperature for pyrene crystal domains to more than double, and even induced pyrene end‐group crystallization in samples that did not exhibit crystals in neat form. It is hypothesized that these features originate from π–π interactions between pyrene ends and GO surfaces. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 159–168 Abstract : Stimuli‐responsive pyrene end‐functionalized poly(dimethyl siloxane) forms pyrene nanocrystals by strong π–π interactions between the polymer ends. The thermal and rheological behavior during various applied thermal stimuli was investigated. Their thermo‐responsiveness was significantly affected by polymer molecular weight which influences pyrene end density. The tunability of their properties by the addition of various additives, including graphene oxide, was explored.