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Radical ring-opening (co)polymerization (RROP) provides an accessible method for synthesizing main chain degradable vinyl polymers. Although the applications of reversible deactivation radical polymerization (RDRP) into RROP have been reported, the use of photo-mediated RDRP methods has received less attention than the thermal process. Here, photo-RROP of the thionolactone dibenzo [c,e]-oxepine-5(7H)-thione (DOT) and methyl acrylate (MA) was studied using photo-iniferter (PI) reversible addition-fragmentation (chain) transfer (RAFT) polymerization at ambient temperature without external radical initiators or photocatalysts. Despite the occurrence of some side reactions including desulfurization-oxygenation and O–S isomerization of DOT promoted by photoexcited thiocarbonyl groups, polymers with thioester linkages in the backbone were prepared, which degraded in the presence of amines and bleach. [Display omitted] • Method for synthesizing main chain degradable vinyl polymers. • Photo-mediated radical ring-opening (co)polymerization. • Copolymerization if thionolactone dibenzo [c,e]-oxepine-5(7H)-thione with methyl acrylate. [ABSTRACT FROM AUTHOR]

It is highly interesting to prepare polyethylene with ultra-high molecular weight under homogeneous conditions by nickel based neutral P^O type catalysts. In this contribution, ligand remote electronic effect was explored in some sterically hindered phosphine-phenolate based neutral nickel catalysts Ni1 – Ni3 to afford UHMWPE. The maximal activity of these catalysts was found to be 1.33 × 106 g mol−1 h−1, which is quite active. The nickel catalysts retained considerable activity at high temperature of 120 °C showing their good thermal stability. More importantly, all these catalysts are capable of generating UHMWPE with maximum M n of 2.51 × 106 g mol−1 by Ni2. The minimum distance between the Ni center and the oxygen of the 2,6-dimethoxy-1,1′-biphenyl unit attached with the phosphorous atom in Ni1 was recorded as 3.154 Å, which exactly matches with the van der Waals radii of oxygen and nickel. This provides an effective shield around the metal by preventing chain transfer and resulting to enhance the molecular weight of polymer. Combined with steric the remote substituents effect also crucial both to modulate activity and molecular weight of polymers. 2,6-dimethoxyaryl unit attached on phosphorous provides an effective shield at the axial place of metal to block the chain transfer process. [Display omitted] • The catalysts Ni1-Ni3 were found highly active with activity up to 1.33 x 106 g·mol-1·h-1. • All catalysts remain active even at 120°C showing their good thermal stability whereas previously reported catalysts of this class usually decompose at 60-80°C. • All the catalysts generate UHMWPE at 60°C with maximum M n up to 2.51 x 106 g·mol-1 by Ni2 , representing a major breakthrough in this class of catalysts. • The minimum distance from the Ni to the oxygen of the 2,6-dimethoxy-1,1'-biphenyl unit to the metallacycle in Ni1 recorded as 3.154 Å which exactly matches with the van der Walls radii. • Catalysts also show considerable incorporation of challenging fundamental polar monomer such as methyl acrylate. [ABSTRACT FROM AUTHOR]

In dielectric nanocomposites, the key issue to reconciling high permittivity and high dielectric ratio is to clarify the underlying mechanism of interfacial dielectric behavior. In this work, we initially investigate how the surface chemistry of SiO 2 may influence interactions with the matrix, the interfacial structure, and the dielectric performance of PMA, then study the effect of the SiO 2 filling content on the structure and performance. We demonstrate that the introduction of SiO 2 can induce the interfacial aggregation of the PMA chains, regulate the local conformation, and thus improve interfacial polarization ability. Too weak attraction arising from sparse hydrogen bonding cannot greatly influence the transformation of molecular conformation to achieve high dielectric permittivity. Excessive interaction originated from the dense hydrogen bonding and interfacial overlapping would anchor the polymer chains on the SiO 2 surface and restrict the activity of dipole reorientation, leading to a negative effect on the dielectric ratio. To achieve an optimal effect of interfacial polarization, we find that the suitable interfacial adhesion energy of SiO 2 is −100∼−110 kJ mol−1 nm−2, which positively impacts both dielectric permittivity and dielectric ratio. On the other hand, if the concentration of SiO 2 is too high, it will produce the interfacial overlapping effect, resulting in the degradation of polarization ability and comprehensive dielectric properties. [Display omitted] • The dielectric enhancement mechanism of SiO 2 /PMA composite is evaluated theoretically. • The special dielectric response is enhanced by reconstruction of chain conformation. • When adhesion strength is 100–110 kJ mol−1 nm−2, SiO 2 particles provide moderate interaction. • The moderate interaction improves permittivity by 78% and dielectric ratio by 42%. • An interfacial overlapping can restrict polarization and reduce dielectric efficiency. [ABSTRACT FROM AUTHOR]

This work is designed to explore the effect of entanglements and particle loading on viscoelastic properties of crosslinked polymer nanocomposites. The entangled and unentangled poly(methyl acrylate) composite networks were synthesized and characterized in linear rheology. We found that the elastic moduli and crosslinking degree of entangled composite networks were unaffected with particle loading. For the unentangled composite networks, both elastic moduli and crosslinking degree enhanced with particle loading. The reinforcement factor analyzed with the recovery of modulus after large deformation indicated that entangled composite networks fully recovered their initial moduli, suggesting the high entanglements can sustain large deformation and maintain their initial chain conformation even at high particle loadings. The unentangled networks did not recover their initial storage moduli after large deformation, posing the non-deformability of the highly crosslinked networks. [Display omitted] • Entangled polymer crosslinking in nanocomposites for enhanced reinforcement is reported. • Particles can enhance crosslinking degree in unentangled (permanent) polymer networks. • Entangled composite networks can fully recover their initial moduli after nonlinear deformation. • The first comparison of unentangled and entangled composite networks. [ABSTRACT FROM AUTHOR]