Weiyu Wang

All acrylic-based thermoplastic elastomers with high upper service temperature and superior mechanical properties

All acrylic-based thermoplastic elastomers (TPEs) offer potential alternatives to the widely-used styrenic TPEs. However, the high entanglement molecular weight (Me) of polyacrylates, as compared to polydienes, leads to “disappointing” mechanical performance as compared to styrenic TPEs. In this study, triblock copolymers composed of alkyl acrylates with different pendant groups and different glass transition temperatures (Tgs), i.e. 1-adamatyl acrylate (AdA) and tetrahydrofurfuryl acrylate (THFA), were synthesized via reversible addition–fragmentation chain transfer (RAFT) polymerization. Thermal characterization of the resulting polymers was performed using differential scanning calorimetry (DSC), and the Tgs of both segments were observed for the block copolymers. This indication of microphase separation behavior was further demonstrated using atomic-force microscopy (AFM) and small angle X-ray scattering (SAXS). Dynamic mechanical analysis (DMA) showed that the softening temperature of the PAdA domains is 123 °C, which is higher than that of both styrenic TPEs and commercial acrylic based TPEs with poly(methyl methacrylate) (PMMA) hard block. The resulting triblock copolymers also exhibited stress–strain behavior superior to that of conventional all acrylic-based TPEs composed of PMMA and poly(n-butyl acrylate) (PBA) made by controlled radical processes, while the tensile strength was lower than for products made by living anionic polymerization.

A General Approach to Access Morphologies of Polyoxometalates in Solution by Using SAXS: An Ab Initio Modeling Protocol

Herein, we reported a general protocol for an ab initio modeling approach to deduce structure information of polyoxometalates (POMs) in solutions from scattering data collected by the small-angle X-ray scattering (SAXS) technique. To validate the protocol, the morphologies of a serious of known POMs in either aqueous or organic solvents were analyzed. The obtained particle morphologies were compared and confirmed with previous reported crystal structures. To extend the feasibility of the protocol to an unknown system of aqueous solutions of Na2 MoO4 with the pH ranging from -1 to 8.35, the formation of {Mo36 } clusters was probed, identified, and confirmed by SAXS. The approach was further optimized with a multi-processing capability to achieve fast analysis of experimental data, thereby, facilitating in situ studies of formations of POMs in solutions. The advantage of this approach is to generate intuitive 3D models of POMs in solutions without confining information such as symmetries and possible sizes.

All-acrylic superelastomers: facile synthesis and exceptional mechanical behavior

All-acrylic multigraft copolymers, poly(butyl acrylate)-g-poly(methyl methacrylate), synthesized using a facile grafting-through methodology, exhibit elongation at break (>1700%) and strain recovery behavior far exceeding those of any commercial acrylic (∼500%) and styrenic (∼1000%) triblock copolymers to date. One-batch anionic polymerization of methyl methacrylate (MMA) using the sec-butyl lithium/N-isopropyl-4-vinylbenzylamine (sec-BuLi/PVBA) initiation system gives PMMA macromonomers with quantitative yield, short reaction time, and using simple synthetic procedures. These new all-acrylic superelastomers and the simple synthetic approach greatly expand the range of potential applications of all-acrylic thermoplastic elastomers (TPEs).

Controlled synthesis of ortho, para-alternating linked polyarenes via catalyst-transfer Suzuki coupling polymerization

A novel class of ortho, para-alternating linked polyarenes is synthesized via catalyst-transfer Suzuki coupling polymerization with Pd2(dba)3/t-Bu3P/p-BrC6H4COPh as initiator. Through a series of kinetic studies and MALDI-TOF analysis, the polymerization is shown to proceed in a chain-growth manner. The optical and thermal properties for the ortho, para-alternating linked polyarenes exhibit unusual molecular weight dependence. Thus, the polymer with lower molecular weight (Mn = 6300 g mol−1) emits green fluorescence whereas the one with higher molecular weight (Mn = 13u2006800 g mol−1) emits blue fluorescence under UV (λ = 360 nm) irradiation. Furthermore, an all-conjugated block copolymer containing a polyfluorene block and the ortho, para-alternating linked block is also successfully prepared, in a one-pot procedure. These results can provide a pathway to obtain polyarenes with precisely controlled structures, hence, desirable properties.

The applications of small-angle X-ray scattering in studying nano-scaled polyoxometalate clusters in solutions

AbstractNano-scaled polyoxometalates (POMs) clusters with sizes ranging from 1 to 10xa0nm attract tremendous attention and have been extensively studied due to POMs’ fascinating structural characteristics and prospects for wide-ranging applications. As a unique class of nanoparticles with well-defined structural topologies and monodispersed masses, the structures and properties of POMs in both bulk state and solutions have been explored with several well-developed protocols. Small-angle X-ray scattering (SAXS) technique, as a powerful tool for studying polymers and nanoparticles, has been recently extended to the investigating of solution behaviors of POMs. In this mini-review, the general principle and typical experimental procedures of SAXS are illustrated first. The applications of SAXS in characterizing POMs’ morphology, counterion distribution around POMs, and short-range interactions among POMs in solutions are highlighted.n Graphical abstractᅟ