Trapping Dynamic Disulfide Bonds in the Hard Segments of Thermoplastic Polyurethane Elastomers

Abstract

Dynamic covalent bonds placed within a polymer chain result in stimulus-responsive materials where the breaking/making and/or exchange of the dynamic bonds controls the response. A key attribute to access such properties is the molecular mobility of the dynamic bonds. The focus of this work is to understand how incorporating a dynamic bond, in the form of disulfide bonds, into the hard phase of a polyurethane will impact the properties of the materials. Thus, uncross-linked polyurethanes with aliphatic disulfide-containing hard segments are synthesized via a two-step protocol, using 2,2′-dithiodiethanol and/or 1,4-butanediol in the second step as the chain extenders. Thermomechanical studies show that, if the dynamic bonds are selectively placed in the hard phase of the polyurethane, the dynamic nature of the disulfide bond can be effectively "switched-off" below the melting temperature of the hard phase. As such the dynamic and mechanical properties of the materials can be controlled by tailoring the nature of the hard phase.

Heat‐triggered poly(siloxane‐urethane)s based on disulfide bonds for self‐healing application

“…The results showed two main stages of the degradation process. The first decomposition occurred around 300–500 °C and involved hard segments which is composed of PU . Hard segments thermal stability of PDMS‐PU samples are similar to the ordinary PU, but soft segments thermal stability of PDMS‐PU samples is better than common PU .…”

Environment‐friendly chemical recycling of aliphatic polyurethanes by hydrolysis in a CO2‐water system

“…Polyurethanes (PUs) are industrially important polymeric materials, which are used for a variety of applications, such as foams and elastomers . Some PUs are responsive to external stimulus, and can be recycled owing to the reversible scission of covalent bonds within the structures . Moreover, the hydrolysis of PUs has been studied as a methodology for chemical recycling.…”

Effect of nano‐silica on gas permeation properties of polyether‐based polyurethane membrane in the presence of esterified canola oil diol as a nucleation agent for hard segments

“…In these polymers, diisocyanate, and chain extender acts as hard segment and polyol acts as soft segment . Due to incompatibility between soft and hard segments, polyurethane shows micro‐phase separation which makes this polymer suitable for variety of applications as foams, paints, coatings, adhesives, elastomers, and and so on . Thus, it is possible to synthesize of a polyurethanes with desirable properties for specific application like gas separation .…”

“…12 Due to incompatibility between soft and hard segments, polyurethane shows micro-phase separation which makes this polymer suitable for variety of applications as foams, paints, coatings, adhesives, elastomers, and and so on. [13][14][15] Thus, it is possible to synthesize of a polyurethanes with desirable properties for specific application like gas separation. 4 In polyurethane membranes for gas separation, hard segment acts as an impermeable phase, while, polyol acts as a permeable phase due to its low glass transition temperature (T g ).…”