Volume 50 Issue 11, November 2018

An ethylene glycol-based hexa-block copolymer with six different temperature-responsive blocks was prepared via a reversible addition-fragmentation chain transfer (RAFT) polymerization. 2-(2-Methoxyethoxy)ethyl methacrylate (MEO₂MA) and oligo(ethylene glycol) methacrylate (OEGMA) were selected as the ethylene glycol-based monomers. Each block exhibits a different LCST in aqueous solution owing to their different OEGMA contents.

The organogels, poly(styrene-co-divinylbenzene); PS gel, poly(styrene-co-divinylbenzene-co-vinylpyridine); PS-VP gel, poly(styrene-co-divinylbenzene-co-vinylbenzoic acid); PS-VBA gel, and poly(styrene-co-divinylbenzene-co-styrenesulfonate); PS-SS gel were prepared with limonene by varying concentration of cross-linker and comonomer to control the gels’ properties. The increase of cross-linker improved the mechanical strength. However, it reduced the solubility in limonene, resulting in the decrease of swelling ratio. The cationic gel shows adsorb ability to anionic compound while anionic gel appears the reverse phenomenon. The limonene organogels were used as lipophilic drug storage and controlled release of testosterone by dense of polymer network.

The grain size was quantitatively evaluated on the free surface, and in the thickness direction. The grain growth on the free surface was very slow in the early stage of thermal annealing, then it shifted to a rapid mode with a power law (~t^0.7). While in the thickness direction, the growth followed a power law of t^1.72 until 1180 min, then it shifted to a slow mode with t^0.21. Furthermore, the oriented layer near the free surface was found to be as thick as 9.5 µm, indicating that grain growth serves as a propagator for the regular ordering of spherical microdomains and orientation of the bcc lattice.

Double helical polysaccharide, xanthan samples with varying molar mass were thermally denatured and renatured in dilute solutions. The molar mass decreased after denaturation and renaturation for samples with an initial molar mass of 10⁶ g mol⁻¹, but those for the samples with an initial molar mass of 10⁵ or 10⁷ g mol⁻¹ decreased only slightly. A model explaining this molar mass dependence of the denaturation and renaturation behaviors was proposed based on the experimental results.

We prepared microwave-responsive adhesives from second-generation acrylic adhesives and ionic liquids, and performed microwave-responsive “on-demand-peeling”. The response depended on the types and quantity of the ionic liquids. While the adhesive strength were maintained irrespective of the contents of ionic liquid in the adhesives, with/without microwave irradiation. The peeling of the adhesives was observed in less than 30 s after microwave irradiation. In this study, we proposed simple, conventional, and attractive preparation of microwave-responsive adhesives by adding ionic liquids.

Nanocomposites composed of mesoporous silica (MPS) materials with various porosity structures (two types of SBA-15 with pores of 4.4 or 8.0 nm, and MCM-41 with pores of 2.9 nm and polypropylene (PP) or functionalized PP containing hydroxyl groups (PPOH) were developed. The nanocomposite containing PPOH and SBA-15 with a pore of 8.0 nm showed higher toughness, stiffness, and transparency than the other nanocomposites.

Nanocomposites containing mesoporous silica (MPS) materials with various pore structures (SBA-15 and MCM-41 types) melt mixed into polypropylene (PP) or PP functionalized with hydroxyl groups (PPOH) were characterized by analytical pyrolysis techniques, such as evolved gas analysis (EGA)-mass spectrometry (MS) and heart-cut EGA-gas chromatography (GC)/MS, to evaluate the interactions between the polymer matrix and MPS and the pore filling of the MPS in the nanocomposite. The EGA-MS measurements revealed that nanocomposites with MPSs evolve specific degradation products, which can be attributed to strong interactions between the polymer molecules and the internal pores. The amount of these specific products increased upon increasing the pore size of the MPS and the hydroxyl content in the polymer matrix. Sufficiently large pores of MPS and high hydroxyl contents in the matrix appear to provide strong interactions because the MPS pores are well-filled with polymer molecules, which contributes to the improved physical properties of the nanocomposites.

Random copolymers of l-lactic acid (LLA) and glycolic acid (GA) [P(LLA-GA)] with LLA unit contents in the ranges of 0–20 and 73–100 mol% were crystallizable during precipitation or melt-crystallization. The GA units of the LLA-rich P(LLA-GA) copolymers were incorporated in a lattice of LLA unit segments, whereas the LLA units of the GA-rich P(LLA-GA) copolymers were incorporated in a lattice of GA unit segments. Even the incorporation of relatively small-sized GA units in relatively large-sized LLA unit segments strongly induced structural disorder in the crystalline lattice.

UV light irradiation causes the unexpected structural transition from core–shell to Janus in droplets consisting of a poly(4-butyltriphenylamine) (PBTPA)/poly(methyl methacrylate) (PMMA) blend solution. We obtained a phase-separated structure formed by the evaporation of the solvent from polymer solution droplets dispersed in an aqueous solution containing a surfactant. It was also found that the transition was caused by UV light with a wavelength of 365 nm, which is mainly absorbed by PBTPA, indicating that this phenomenon is triggered by PBTPA.