Research articles

Dissolved polymers directed molecular crystallization behavior under dilute and crowding conditions. Larger poly(ethylene glycol)s (PEGs) accelerated caffeine crystal formation in the dilute regime of PEG solutions, which was attributed to the depletion attraction that promoted caffeine cluster aggregation into crystal nuclei. In the semidilute regime, the crystal formation rate was insensitive to the molecular weight of PEGs. This observation was consistent with polymer blob properties, which govern depletion attraction and maintain a constant size at a given polymer concentration, irrespective of molecular weight in the semidilute regime.

The silicone rubber materials with foam/solid alternating multilayered structure have been constructed by combining two methods of the multilayered hot-pressing and supercritical carbon dioxide (SCCO₂) foaming. The growth of the cell is restrained by the solid layer, resulting in a decrease of the cell size. In addition, the introduction of the solid layer can effectively improve the mechanical properties of the microcellular silicone rubber foam. The experimental results are analyzed by finite element analysis (FEA).

Thin film aromatic polyimides were quantitatively analyzed by grazing-incidence X-ray diffraction (GI-XRD), variable-temperature infrared p-polarized multiple-angle resolution spectroscopy (VT-pMAIRS), and spectroscopic ellipsometry (SE) methods. Combining VT-pMAIRS and GI-XRD revealed characteristic heterogeneous structures comprising non-oriented amorphous and oriented liquid-crystalline glass regions. Additionally, SE indicated that the film involved anisotropic-shaped void inducing form-birefringence. Such an excess of birefringence can make it difficult to estimate orientational order using birefringence measurement. This methodology presented here will remarkably contribute to general structural analyses of all intriguing thin-film polymers with characteristic heterogeneity.

A dinuclear Pd(II) complex possessing a cyclic ligand was applied as a coordinative cross-linker of acrylonitrile–butadiene rubber (NBR). Tensile tests revealed that the mechanical properties of the coordinatively cross-linked NBRs were improved compared with those of the original NBR. Increasing the loading amount of the complex enhanced Young’s modulus, tensile strength, tensile strain, and toughness. The cross-linked NBR could be reused with a simple dissolution and drying process, which featured coordinative cross-linking.

We report a novel approach of siloxane bond splitting in organosiloxane using mixture of tris(pentafluorophenyl)borane and dimethyl carbonate. In the first part of this note, depolymerization of polydimethylsiloxane by dimethyl carbonate and with the addition of tris(pentafluorophenyl)borane is studied. Reactions are studied at different concentrations of above-mentioned reagents and temperature while the second part of this note represents theoretical calculation results which explain the mechanism of the depolymerization reaction.

Amphiphilic thermoresponsive copolymer bottlebrushes based on methoxy oligo(ethylene glycol) methacrylate (MOEGM) and alkoxy(C₁₂-C₁₄) oligo(ethylene glycol) methacrylate (DOEGM) have been synthesized via RAFT and conventional free-radical polymerization in toluene. In water, these copolymer brushes form flower-like micelles with a hydrophobic core consisting of a polymer backbone and alkyl(C₁₂–C₁₄) groups and poly(ethylene glycol) linear chains and loops forming a hydrophilic shell. The size and aggregation number of the micelles depend on the copolymer composition and chain length, as well as on the synthesis method.

As a surface modifier, poly[oligo(2-ethyl-2-oxazoline) methacrylate] (P[O(Ox)_nMA]) with two different degrees of polymerization (n = 7 and 19) of the side chain were mixed into poly(methyl methacrylate) (PMMA). Once the PMMA/P[O(Ox)_nMA] films contacted with water, the surface was reorganized due to the migration of P[O(Ox)_nMA]. The extent of the surface segregation was more remarkable for P[O(Ox)₇MA] than P[O(Ox)₁₉MA] due to the entropic factor, resulting that the fibroblast adhesion on the film were much better suppressed for P[O(Ox)₇MA] than P[O(Ox)₁₉MA].

A facile modification method for a commercial polyethylene membrane separator using a cross-linked single-ion conducting polymer network with a highly delocalized anionic group was developed. A cross-linker, poly(ethylene glycol) diacrylate, and a delocalized anionic monomer, lithium (4-styrenesulfonyl)(trifluoromethanesulfonyl)imide, were used to modify the surface of the polyethylene separator via UV-initiated polymerization. The resulting polymer coating improves the electrolyte wettability and suppresses the diffusion of anionic species across the separator. The effect of the polymer modification of the separator on the electrochemical properties of nonaqueous Li-O₂ cells was investigated.

Using polymerase chain reaction (PCR)-mediated recombination, we prepared single ribonucleic acid (RNA) chains containing bifunctional RNA sequences involving substrate binding and phosphorescent signaling. The prepared RNAs largely maintained the functionalities of the original aptamers even after bifunctionalization. We demonstrated that the bifunctionalized RNAs can be used as phosphorescent detection probes for the target protein. Therefore, we suggested that the PCR-mediated “one stroke drawing” is a promising strategy for the preparation of RNA detection probes.

Poly(methacrylated vanillin) (PMV) was investigated for its reactivity in multicomponent reactions as a reactive polymer that can be sourced from lignin-based components. The Passerini three-component reaction (Passerini-3CR) of the PMV in solution phases revealed that the PMV pendant aldehydes can be converted into the corresponding α-acyloxy amides with >90% conversions under the optimized conditions. Taking advantage of this high reactivity of PMV in solution phase, its immobilized cellulose fabric (Cell-g-PMV), a wood biomass-sourced organic hybrid, was subjected to the Passerini-3CR, enabling an engraftment of carboxylic acid and isocyanide components on the cellulose-based fabrics.

The salt addition affects the structure and properties of poly(vinyl alcohol) films as it reduces the hydrogen bonding in PVA chains and decreases the crystallinity. Consequently, the T_g shifts to low temperatures, and the modulus beyond T_g decreases markedly. This study confirmed that the impact of bromine salts on the structure and properties followed the order of Hofmeister series, i.e., Li⁺ > Na⁺  > K⁺. Although cations play an important role, the data obtained also demonstrated that the strong ion–dipole interactions between anions and PVA chains have a significant impact on the crystallinity and T_g.