Ring-Opening Metathesis Polymerization for the Synthesis of Terpenoid-Based Pressure-Sensitive Adhesives.

Pressure-sensitive adhesives (PSAs) made from norbornene-functionalized terpenoid-based monomers are reported as a possible alternative to the conventional petrochemically based PSAs. For this, tetrahydrogeranyl, menthyl, and isobornyl norbornenate monomers, with a renewable carbon content up to 72%, are synthesized and copolymerized via ring-opening metathesis polymerization (ROMP) with cyclooctadiene and 5-norbornene-2-carboxylic acid. ROMP enables a much faster and controlled polymerization process in comparison to free radical polymerization techniques when targeting high molecular weights and therefore unlocks a potential to design a unique class of PSA materials. The moduli at bonding and debonding frequencies of the obtained PSAs are plotted in the Chang classification system and are used to predict their adhesive performance. Tack and peel measurements indicate that the terpenoid-based norbornenate formulations show similar adhesive properties in comparison to the previously investigated acrylic counterparts.

Chemical control of the viscoelastic properties of vinylogous urethane vitrimers.

Vinylogous urethane based vitrimers are polymer networks that have the intrinsic property to undergo network rearrangements, stress relaxation and viscoelastic flow, mediated by rapid addition/elimination reactions of free chain end amines. Here we show that the covalent exchange kinetics significantly can be influenced by combination with various simple additives. As anticipated, the exchange reactions on network level can be further accelerated using either Brønsted or Lewis acid additives. Remarkably, however, a strong inhibitory effect is observed when a base is added to the polymer matrix. These effects have been mechanistically rationalized, guided by low-molecular weight kinetic model experiments. Thus, vitrimer elastomer materials can be rationally designed to display a wide range of viscoelastic properties.

Aqueous copper-mediated living radical polymerisation of N-acryloylmorpholine, SET-LRP in water.

The polymerisation of N-acryloylmorpholine in water is reported utilising Cu(0)-mediated living radical polymerisation (SET-LRP). The inherent instability of [Cu(I) (Me6-Tren)Br] in aqueous solution is exploited via rapid disproportionation to prepare Cu(0) particles and [Cu(II) (Me6-Tren)Br2 ] in situ prior to addition of monomer and initiator. Quantitative conversion is attained within 30 min for various degrees of polymerisation (DPn = 20-640) with SEC showing symmetrical narrow molecular weight distributions (D < 1.18) in all cases. Optimised conditions are subsequently applied for the preparation of a diblock copolymer poly(NIPAm)-b-(N-acryloylmorpholine), illustrating the versatility of this approach.