Abstract
Supramolecular polymers are important within a wide range of applications including printing, adhesives, coatings, cosmetics, surgery, and nano-fabrication. The possibility to tune polymer properties through the control of supramolecular associations makes these materials both versatile and powerful. Here, we present a systematic investigation of the linear shear rheology for a series of unentangled ethylhexyl acrylate-based polymers for which the concentration of randomly distributed supramolecular side groups is systematically varied. We perform a detailed investigation of the applicability of time temperature superposition (TTS) for our polymers; small amplitude oscillatory shear rheology is combined with stress relaxation experiments to identify the dynamic range over which TTS is a reasonable approximation. Moreover, we find that the “sticky-Rouse” model normally used to interpret the rheological response of supramolecular polymers fits our experimental data well in the terminal regime, but is less successful in the rubbery plateau regime. We propose some modifications to the “sticky-Rouse” model, which includes more realistic assumptions with regard to (i) the random placement of the stickers along the backbone, (ii) the contributions from dangling chain ends, and (iii) the chain motion upon dissociation of a sticker and reassociation with a new co-ordination which involves a finite sized “hop” of the chain. Our model provides an improved description of the plateau region. Finally, we measure the extensional rheological response of one of our supramolecular polymers. For the probed extensional flow rates, which are small compared to the characteristic rates of sticker dynamics, we expect a Rouse-type description to work well. We test this by modeling the observed strain hardening using the upper convected Maxwell model and demonstrate that this simple model can describe the data well, confirming the prediction and supporting our determination of sticker dynamics based on linear shear rheology.
Highlights
INTRODUCTIONInteresting and useful temperature sensitivity of the interactions [23,48]. Supramolecular polymers based on UPy groups have been widely investigated and materials with important characteristics such as stimuli-responsive [23], self-healing [10,11,49,50,51,52], and temperature responsive [53,54] properties have found applications within printing [55,56,57,58], cosmetics [59,60], adhesives [61], and coatings [62]
Previously been investigated [20,63,64,65,66]
To obtain the small amplitude oscillatory shear (SAOS) response over a wider frequency range than what is possible in a single measurement, we investigate in detail to what extent temperature superposition (TTS) can be used to extend the dynamic range
Summary
Interesting and useful temperature sensitivity of the interactions [23,48]. Supramolecular polymers based on UPy groups have been widely investigated and materials with important characteristics such as stimuli-responsive [23], self-healing [10,11,49,50,51,52], and temperature responsive [53,54] properties have found applications within printing [55,56,57,58], cosmetics [59,60], adhesives [61], and coatings [62]. We focus on four particular aspects of the rheology of our samples: (i) the effects of adding UPy-based side groups on the linear viscoelasticity, (ii) a detailed investigation of the extent to which TTS can be applied to our series of polymers, where we complement our small amplitude oscillatory shear (SAOS) experiments with measurements of stress relaxation resulting from a step shear strain; here, the time-dependent response is converted to the frequency domain to extend the frequency range accessed at a single temperature, (iii) detailed modeling of the linear rheological response using both a standard and a modified version of the sticky-Rouse model, and (iv) extensional rheology measurements on one of our supramolecular polymers, UPyPEHA6, together with modeling using a simple upper convected Maxwell modeling which is expected to be applicable for extensional flow rates where Rouse-like dynamics are relevant
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
