Abstract
Thermo-reversible supramolecular networks from polyisoprene-block-polystyrene-block-polyisoprene (ISI) triblock copolymers with short, functionalized polyisoprene (PI) blocks were investigated. Functional groups along the PI blocks were hydroxyl groups, ester groups with a carboxylic end-group (-O-CO-CH2-CH2-COOH), and urethane groups with an amine end-group—synthesized from various types of diamines—(-O-CO-NH-R-NH2). Dynamic mechanical analysis (DMA) was performed at temperatures above Tg of polystyrene (PS) to investigate the influence of the different functional groups, the molecular weight, and the composition of the triblock copolymers on the materials’ properties. Furthermore, comparisons to DMA results of diblock copolymers, modified in the same way, will be presented. Arising reversible and irreversible processes observed during DMA experiments will be compared to results from temperature-dependent Fourier transform infrared (FTIR) spectroscopy. For the elaborated systems, the transition from reversible, hydrogen-bonded to permanently cross-linked networks was observed at around 150 °C.
Highlights
Control over reversible polymer networks is becoming more and more important in developing new materials with outstanding characteristics [1,2,3,4,5]
Notation of block copolymers is written as Ix Sy Iz M
The end-block functionalization of polyisoprene-block-polystyrene-block-polyisoprene triblock copolymers leads to significant changes in mechanical behavior
Summary
Control over reversible polymer networks is becoming more and more important in developing new materials with outstanding characteristics [1,2,3,4,5]. Reversible covalent bonds [12,14] as used in vitrimers [2,15,16,17,18] or, for example, via a (retro-)Diels–Alder reaction [14,19,20] are investigated. Both modification approaches—covalently and non-covalently bonded—can build polymer-like arrangements consisting of lower-molecular-weight building units. Polymeric networks are present, and characteristics of high-molecular-weight polymers predominate.
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