Structural analysis of core-shell type polymer particles composed of poly(butyl acrylate) and poly(methyl methacrylate) by high-resolution solid-state 13C n.m.r. spectroscopy

Simultaneously improving the ductility and strength of aromatic thermoset films

Aromatic thermoset materials have shown great potential applications in various fields owing to their excellent mechanical strengths. However, their poor ductility is still hinders their large-scale applications. In this study, a new class of aromatic thermosets consisting of two types of crosslinks was successfully developed by incorporating the special group imidazole into a type of crosslinked thermoset. One crosslink is constituted of reversible multiple noncovalent interactions containing “face-face” π–π stacking, “point-point” hydrogen bonds, and ion-pair electrostatic interactions, whereas the other is composed of permanent covalent bonds. Most importantly, the synergetic interplay among these reversible multiple noncovalent interactions enables them to evade the restrictions from the aromatic polymer skeletons to proceed with their dynamic dissociating-rebuilding processes, which can timely and effectively dissipate the internal stress. Finally, owing to the coefficient of these two types of crosslinks, a significantly enhanced ductility was successfully obtained on these aromatic thermosets and their tensile strengths were also improved. Such thermosets having simultaneously enhanced strengths and ductility are predicted to be eventually used in a wide range of applications.

Nanostructured composites obtained by ATRP sleeving of bacterial cellulose nanofibers with acrylate polymers

Novel nanostructured composite materials based on bacterial cellulose membranes (BC) and acrylate polymers were prepared by in situ atom transfer radical polymerization (ATRP). BC membranes were functionalized with initiating sites, by reaction with 2-bromoisobutyryl bromide (BiBBr), followed by atom transfer radical polymerization of methyl methacrylate (MMA) and n-butyl acrylate (BA), catalyzed by copper(I) bromide and N,N,N',N″,N″-pentamethyldiethylenetriamine (PMDETA), using two distinct initiator amounts and monomer feeds. The living characteristic of the system was proven by the growth of PBA block from the BC-g-PMMA membrane. The BC nanofiber sleeving was clearly demonstrated by SEM imaging, and its extent can be tuned by controlling the amount of initiating sites and the monomer feed. The ensuing nanocomposites showed high hydrophobicity (contact angles with water up to 134°), good thermal stability (initial degradation temperature in the range 241-275 °C), and were more flexible that the unmodified BC membranes.