Surprisingly, a few seconds–minutes of compression at room temperature can increase the rate of dynamic bond exchange as measured by better self-healing, even for thermoresponsive dynamic bonds which do not exchange under ambient conditions.

Peak assignments of the Fourier-transform infrared spectra and solution NMR spectra of the synthesized SMADs and representative TEM images of SMADLPs made from POPC liposomes (PDF)

Phenyl vinyl ketone (PVK) is known for its responsiveness to light, with initiation promoted under visible light and degradation of poly­(PVK) promoted under UV radiation. Thus, expensive radical sources such as photocatalysts and initiators can be substituted by PVK to promote intrinsic photoinitiation giving well-defined polymers. Homo polymers and block copolymers are readily synthesized by reversible deactivation radical polymerization techniques; this study is the first approach of formation of block polymers through the intrinsically generated radicals of PVK monomers, where the monomer serves as both the chain forming unit and the radical source. In this work, the photoinitiation of PVK was used to generate poly­(PVK) homopolymers, which were chain extended with butyl acrylate (BA) and PVK to synthesize poly­(PVK-BA-PVK) block polymers. The structural differences of PVK and BA caused microphase separation of the block segments to form thermoplastic elastomers (TPEs) with interesting thermomechanical properties. Due to the differences in glass transition temperature, the poly­(PVK) blocks formed the hard segments of the TPE, with the poly­(BA) segments forming the soft elastic domains. The TPE materials could achieve a maximum of 1000 kPa stress and 400% strain at break. Irradiation of the TPE materials with 310 nm UV light promoted the degradation of poly­(PVK) segments, with associated changes such as a decrease in mechanical strength and elasticity. Molecular dynamics simulations confirmed the trends observed in TPE mechanical properties with the changes in the polymer composition. Further, the simulations provided atomistic insights into the underlined degradation mechanism of PVK in block polymers and its effect on TPE mechanical properties.

Dynamic materials are known for their self-healing, adhesive, and shape memory applications. Interpenetrating networks (IPNs) are types of materials that can hold dual-dynamic crosslinkers to show complementary chemical and mechanical properties. There have been a number of research studies exploring the dynamic chemistries involved in IPN materials. Not only the bond type but also the polymer network architecture play an important role in governing IPN material properties. In this study, we show that network architectural features are as much as important as studying the dynamic chemistries using an IPN system with quadrupole hydrogen (H) bonding and thiol-Michael (TM) bonding. This work varied network types, chain lengths, dynamic bond compositions, crosslink densities, and crosslink distributions within a system to explore their effects on the thermomechanical properties. The synergetic effects of H and TM bonds revealed excellent stress relaxation and self-healing at room temperature and elevated temperatures. Increment of chain length and crosslink density enhanced the strength of the materials to as high as 3.5 MPa, while the crosslink distribution boosted the creep resistance under an applied force. Furthermore, complementary H and TM bonding assisted in improving the adhesive properties in these materials to hold up to 2 kg weight with the adhered wood strips.

The power of chemical light generation (chemiluminescence) is used to drive polymerization reactions. A biphasic reaction is developed such that light‐generating reactions are confined to the organic phase and photopolymerization occurs in the aqueous phase. Well‐defined RAFT‐capped polymers are synthesized and the kinetics are shown to be dictated by light generation.