Volume 54 Issue 5, May 2022

Our work studied the effect of proteins on the graft copolymerization of vinyltriethoxysilane (VTES) on natural rubber (NR) latex. Stress at break of the graft copolymers was substantially higher when proteins were present; that is, the stress at break of fresh NR-graft-PVTES was higher than that of protein-free NR-graft-PVTES. Silica nanomatrix was formed more visibly in the presence of proteins, as observed by transmission electron microscopy. Furthermore, proteins were found to accelerate the formation of silica particles by forming hydrogen bonds with VTES molecules and enhancing hydrolysis with water molecules.

The anionic polymerization behavior of phenyl-substituted [3]dendralene derivatives, 2-phenyl[3]dendralene (2-P3D) and (Z)-1-phenyl[3]dendralene (1Z-P3D), was theoretically investigated using DFT calculation. The kinetic analysis based on the activation Gibbs free energy of the chain propagation showed that the anionic polymerization of 1Z-P3D proceeded with highly regioselective character; however, that of 2-P3D did not. By conformational and molecular orbital analyses, it was suggested that an effective conjugation of phenyl substituent with the chain end carbanion had a significant effect in the regioselectivity of the anionic polymerization of phenyl-substituted [3]dendralene derivatives.

For bulk crystallization, the growth rate is governed by the nucleation process and depends mainly on the crystallization temperature and composition of the blends. If the crystallization process is confined in ultrathin films, then the diffusion-controlled growth process is remarkably retarded due to the thickness confinement. The longitudinal and lateral growth rates of basal and overgrown lamellar crystals shows different. This study reports the film thickness significantly retards the growth rate of basal and overgrown lamellar crystals and reduces the number of overgrowths on the basal lamellar crystals.

In the polypropylene (PP)/carbon fiber (CF) composite, it has been well known that maleic acid modified PP (MAPP) improves the interfacial adhesion with CF. However, the effect of maleic acid modification on the PP crystals around CF, and that of the PP crystals on the interfacial adhesion have not been clarified well. In this study, the local crystal structure of PP near CF was investigated using micro-Raman spectroscopy, and it was demonstrated that the crystal growth of PP near CF contributes significantly to the interfacial adhesion.

Sum-frequency generation (SFG) spectroscopy is a powerful tool for studying the molecular orientation in confined systems based on the second-order nonlinear optical effect. Here, we demonstrated the SFG imaging for films of uniaxially-oriented poly(vinylidene fluoride) (PVDF) and spin-coated isotactic polypropylene (iPP). The orientational difference of lamellar fibrils in the two films was identified.

A poly(styrene)(PS)-b-poly(methyl methacrylate)(PMMA)-b-PS triblock copolymer was successfully solubilized as single chains to form PS single-block particles at either end without aggregation of the PS blocks in poly(n-nonyl acrylate)(PNA) and PMMA Langmuir monolayers, which both form miscible monolayers with the middle PMMA block. The end-to-end distance was evaluated using the PS single-block particles at either end, and the PMMA block chain was not found to be highly segregated in either the PNA and PMMA monolayers but was rather elongated and interpenetrated with the matrix chains.

The deformed BPEP/GR with a 3D structure rapidly recovered to a 2D film by remote NIR irradiation. Furthermore, because the crystal structure of the biphenyl unit can be regulated through rapid polymerization, thermal treatment is applicable. The activation and recombination of the biphenyl units and the NIR responsiveness results in the self-folding behavior of BPEP/GR under NIR laser irradiation. It is also recognized as a reconfigured permanent shape, which can be recovered under a thermal stimulus.

Poly(3,4-ethylenedioxythiophene) doped with poly(4-styrene sulfonate) (PEDOT: PSS) films have strong potential for application in flexible transparent conductive electrodes. In this study, the electrical conductivity of PEDOT: PSS is shown to be enhanced by a bisphenol additive, bis (4-hydroxyphenyl) sulfone (BPS). The effects of BPS on the chemical structure of PEDOT: PSS were investigated using X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy. The PEDOT: PSS conformation is found to undergo a transformation into a highly conductive structure following the addition of BPS.

The pH-responsive behavior of a core-crosslinked multiarm star polymer with an ionic poly(acrylic acid) (PAA) block segment in the arm was greatly affected by the arm chain sequence. Two types of star polymers with opposite block sequences was shown to differ sharply in the balance of hydrogen bonding and ionic repulsion between arm polymers, resulting in the different pH-responsive aggregation behaviors. The fundamental understanding gained by the present study deepens the insight into the solution properties of branched polyelectrolytes, which would expand the possibility for various applications.

Polymer and composite synthesis and structures. Formation of Graphene Matrix in Natural Rubber Dispersoid. In this study, the preparation of and characterization of a composite of natural rubber (NR) discontinuous phase (dispersoid) and graphene continuous phase (matrix) were carried out. Graphene (G) was prepared and grafted on rubber particle in latex stage in the presence of initiator tert-butylhydroperoxide and tetraethylene pentaamine with optimal amount of surfactant. The structure, the morphology, the mechanical properties, and the electromagnetic shielding of the resulting materials were superior compared to that of NR/graphene blend.

All-cellulosic robust composite directly made from cellulose acetate (CA) and nanofibrillated bacterial cellulose (NFBC) sol was developed in this study. The key processes were utilizing a water/organic mixed solvent, for example, acetone, to maintain a good dispersion of the NFBC and good dissolution of CA, along with evaporating this mixed solvent without significant aggregation of the NFBC. Both CA and NFBC can be made from agricultural waste by combining chemical and biochemical processes. The CA/NFBC composite thus prepared is one of the promising green materials in the near future.

PVDF is a promising candidate material for fabricating superhydrophobic surfaces because of its intrinsic low surface free energy, chemical resistance, and thermal stability. In this work, we investigated how morphologies influenced the surface wettability of PVDF nanostructure assembly coatings. The coatings consisting of PVDF nanoparticles exhibited highly improved hydrophobicity compared with that of the flat drop-coating PVDF surface. These results provide valuable insight into PVDF surface design, especially for superhydrophobic coatings.