We report the synthesis and characterization of a kinetically controlled, thermoreversible supramolecular polyurethane whose mechanical properties depend unusually strongly on the processing history. Materials were prepared by solution casting, quenching and annealing of quenched material, allowing pronounced micro-structural evolution, which leads to rapid increases in modulus as determined by rheological analysis. Tensile tests showed that the quenched material is soft, weak and ductile (shear modulus ~ 5 MPa, elongation ~ 250 %), but after annealing, at 70 °C for one hour, it becomes stiffer, stronger and more brittle (~ 20 MPa, ~ 20 %). FTIR and NMR spectroscopic analysis, coupled with MDSC and SAXS, were performed to investigate the network's dynamic structural changes. SAXS results suggest the presence of a lamellar structure in the sample when solution cast at high temperature, or annealed. This ordering is unique when compared to structurally-related supramolecular bisurethane and bisurea polymers, and may be the cause of the observed path dependence. These mechanical properties, which can be switched repeatedly by simple thermal treatments, coupled with its adhesion properties as determined from peel and tack tests, make it an excellent candidate as a recyclable material for adhesives and coatings.

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Porous Polyimides (pPIs) represent a fascinating class of porous organic polymers (POPs). Not only do they exhibit high thermal and chemical stabilities, high surface areas, and energy storage capabilities, but...

The alternating sequenced copolymer poly-(methacrylic acid-alt-hydroxyethyl acrylate), p­(MAA-alt-HEA), was recently found to display a lower critical solution temperature (LCST) behavior in 1,2-dimethoxyethane (DME), whereas the random copolymer of the same average molecular weight and composition did not. As an effort to understand this peculiar behavior, we investigated solutions of both corresponding homopolymers, poly­(methacrylic acid) (pMAA) and poly­(2-hydroxyethyl acrylate) (pHEA), in DME. We found that in the same temperature range, concentration, and degree of polymerization, pHEA is fully soluble, whereas pMAA shows the LCST behavior similar to the alternating copolymer. On the basis of Hansen’s parameters of the homopolymers, it would be predicted that neither should dissolve in DME. Solubility is therefore connected to specific solvent–polymer interactions and more specifically to the formation of a polymer–solvent complex via hydrogen bonds. We designed a method which combines mid-infrared (MIR) and near-infrared (NIR) spectroscopy in solution to study hydrogen bonding as a function of temperature (by MIR) with simultaneous monitoring of LCST (by NIR). In parallel, the global shape of polymer chains and aggregates was characterized by small-angle neutron scattering in deuterated DME. It is found that pMAA chains form aggregates upon increase of temperature through formation of cyclic H-bonded dicarboxylic dimers. As for pHEA, the solvent’s quality of DME slightly decreases with temperature, but aggregation is prevented by entropic repulsion of the flexible side chains. We thus concluded that nonoccurrence of LCST in the random copolymer is due to the presence of pHEA homoblocks that maintain constant solubility over the whole temperature range.