Correction: Mechanochemical tools for polymer materials.

Correction for 'Mechanochemical tools for polymer materials' by Yinjun Chen et al., Chem. Soc. Rev., 2021, 50, 4100-4140, DOI: 10.1039/D0CS00940G.

Mechanochemical tools for polymer materials.

Mechanochemistry provides a unique approach to investigate macroscopic deformation, failure and healing of polymer materials. The development of mechanophores - molecular units that respond to mechanical force - has been instrumental in the success of this endeavor. This review aims to provide a critical evaluation of the large variety of mechanophores reported in literature, and to assess the molecular and macroscopic factors that determine their activation. Applications in materials science are highlighted, and challenges in polymer mechanochemistry are discussed.

Unexpected thermo-responsiveness of bisurea-functionalized hydrophilic polymers in water.

HYPOTHESIS: Thermoresponsive polymers are important materials for various applications. However, the number of polymers that exhibit this property in the temperature range of interest remains limited. The development of novel rational design strategies through the understanding of the thermal transition's origin is therefore of utmost importance. EXPERIMENTS: Bisurea-functionalized water-soluble polymers were synthesized by RAFT polymerization. After direct dissolution in water, the supramolecular assemblies were analyzed by cryo-TEM and SANS. Their temperature-dependent water-solubility was characterized by various techniques, namely DLS, SANS, DSC, IR, to understand the origin of the temperature sensitivity. FINDINGS: The supramolecular assemblies exhibit an unexpected temperature-dependent solubility. For instance, a cloud point of only 39 °C was measured for poly(N,N-dimethylacrylamide) assemblies. This property is not restricted to one specific polymer but is rather a general feature of bisurea-functionalized polymers that form supramacromolecular bottlebrushes in water. The results highlight the existence of two distinct transitions; the first one is a visually perceptible cloud point due to the aggregation of individual micelles, presumably driven by the hydrophobic effect. The second transition is related to the dissociation of intermolecular bisurea hydrogen bonds. Finally, we show that it is possible to widely tune the cloud point temperature through the formation of co-assemblies.

Beyond Simple AB Diblock Copolymers: Application of Bifunctional and Trifunctional RAFT Agents to PISA in Water.

The influence of the macromolecular reversible addition-fragmentation chain transfer (macro-RAFT) agent architecture on the morphology of the self-assemblies obtained by aqueous RAFT dispersion polymerization in polymerization-induced self-assembly (PISA) is studied by comparing amphiphilic AB diblock, (AB)2 triblock, and triarm star-shaped (AB)3 copolymers, constituted of N,N-dimethylacrylamide (DMAc = A) and diacetone acrylamide (DAAm = B). Symmetrical triarm (AB)3 copolymers could be synthesized for the first time in a PISA process. Spheres and higher order morphologies, such as worms or vesicles, could be obtained for all types of architectures and the parameters that determine their formation have been studied. In particular, we found that the total DPn of the PDMAc and the PDAAm segments, i.e., the same overall molar mass, at the same Mn (PDMAc)/Mn (PDAAm) ratio, rather than the individual length of the arms determined the morphologies for the linear (AB)2 and star shaped (AB)3 copolymers obtained by using the bi- and trifunctional macro-RAFT agents.

Templated PISA: Driving Polymerization-Induced Self-Assembly towards Fibre Morphology.

Dispersions of block copolymer fibres in water have many potential applications and can be obtained by polymerization-induced self-assembly (PISA), but only under very restricted experimental conditions. In order to enlarge this experimental window, we introduced a supramolecular moiety, a hydrogen-bonded bis-urea sticker, in the macromolecular reversible addition fragmentation chain transfer (RAFT) agent to drive the morphology of the nano-objects produced by RAFT-mediated PISA towards the fibre morphology. This novel concept is tested in the synthesis of a series of poly(N,N-dimethylacrylamide)-b-poly(2-methoxyethyl acrylate) (PDMAc-b-PMEA) diblock copolymers prepared by dispersion polymerization in water. The results prove that the introduction of the templating bis-urea stickers into PISA greatly promotes the formation of fibres in a large experimental window.