Highly efficient grafting of hetero-complementary amidinium and carboxylate hydrogen-bonding/ionic pairs onto polymer surfaces

We describe a grafting methodology, based on thiol-fluoroarene chemistry, to efficiently incorporate complementary hydrogen-bonding carboxylate and amidinium groups into polymer backbones. The process was optimized both in solution and on the surface of processed films, with the aim to produce materials showing hetero-complementary adhesion.

Bioinspired Underwater Adhesives by Using the Supramolecular Toolbox

Nature has developed protein-based adhesives whose underwater performance has attracted much research attention over the last few decades. The adhesive proteins are rich in catechols combined with amphiphilic and ionic features. This combination of features constitutes a supramolecular toolbox, to provide stimuli-responsive processing of the adhesive, to secure strong adhesion to a variety of surfaces, and to control the cohesive properties of the material. Here, the versatile interactions used in adhesives secreted by sandcastle worms and mussels are explored. These biological principles are then put in a broader perspective, and synthetic adhesive systems that are based on different types of supramolecular interactions are summarized. The variety and combinations of interactions that can be used in the design of new adhesive systems are highlighted.

An adhesive elastomeric supramolecular polyurethane healable at body temperature

In this paper, we report the synthesis and healing ability of a non-cytotoxic supramolecular polyurethane network whose mechanical properties can be recovered efficiently (>99%) at the temperature of the human body (37 °C). Rheological analysis revealed an acceleration in the drop of the storage modulus above 37 °C, on account of the dissociation of the supramolecular polyurethane network, and this decrease in viscosity enables the efficient recovery of the mechanical properties. Microscopic and mechanical characterisation has shown that this material is able to recover mechanical properties across a damage site with minimal contact required between the interfaces and also demonstrated that the mechanical properties improved when compared to other low temperature healing elastomers or gel-like materials. The supramolecular polyurethane was found to be non-toxic in a cytotoxicity assay carried out in human skin fibroblasts (cell viability > 94% and non-significantly different compared to the untreated control). This supramolecular network material also exhibited excellent adhesion to pig skin and could be healed completely in situ post damage indicating that biomedical applications could be targeted, such as artificial skin or wound dressings with supramolecular materials of this type.

Microphase separation induced in the melt of Pluronic copolymers by blending with a hydrogen bonding urea-urethane end-capped supramolecular polymer

Blending with a hydrogen-bonding supramolecular polymer is shown to be a successful novel strategy to induce microphase-separation in the melt of a Pluronic polyether block copolymer. The supramolecular polymer is a polybutadiene derivative with urea-urethane end caps. Microphase separation is analysed using small-angle X-ray scattering and its influence on the macroscopic rheological properties is analysed. FTIR spectroscopy provides a detailed picture of the inter-molecular interactions between the polymer chains that induces conformational changes leading to microphase separation.

Supramolecular polymer adhesives: advanced materials inspired by nature

Due to their dynamic, stimuli-responsive nature, non-covalent interactions represent versatile design elements that can be found in nature in many molecular processes or materials, where adaptive behavior or reversible connectivity is required. Examples include molecular recognition processes, which trigger biological responses or cell-adhesion to surfaces, and a broad range of animal secreted adhesives with environment-dependent properties. Such advanced functionalities have inspired researchers to employ similar design approaches for the development of synthetic polymers with stimuli-responsive properties. The utilization of non-covalent interactions for the design of adhesives with advanced functionalities such as stimuli responsiveness, bonding and debonding on demand capability, surface selectivity or recyclability is a rapidly emerging subset of this field, which is summarized in this review.

Development of solvent-free synthesis of hydrogen-bonded supramolecular polyurethanes

A solvent free ball-milling method for the synthesis of small molecule and oligomeric carbamates is described that is applicable to supramolecular polymer synthesis.

In this work we describe the solvent free synthesis of supramolecular polyurethanes held together by heterocomplementary triple hydrogen bonding. We perform a systematic evaluation on the base catalyzed synthesis of small molecule ureas and carbamates from a range of isocyanates, amines and alcohols in solution and in the solid state using ball milling. These optimized procedures are then shown to be applicable to the synthesis of supramolecular polyurethanes using solvent-free methods.