Model catalysts having specially designed active species on support surfaces were employed to understand relationships between the structure/state of active sites and their catalytic performances for two classes of industrial olefin polymerization catalysts: Ziegler‐Natta and Phillips catalysts. Propylene polymerization using a TiCl3/MgCl2 model Ziegler‐Natta catalyst clarified an important role of the Ti dispersion state for the polymer stereo & chemical structures. Model Phillips catalysts having monochromate and dichromate structures on silica support imparted knowledge that dinuclear species is more responsible for the production of α‐olefin comonomer in ethylene polymerization, thus giving more branched polyethylene.

An improved stopped‐flow (SF) technique is employed to clarify the origin of kinetics in propylene polymerization with a Mg(OEt)2‐based Ziegler–Natta catalyst. Polymerization in the range of 0.1–5 s exhibits a kinetic transition from a linear development to a build‐up‐type development of the yield. It is found that a lower alkylaluminum concentration leads to a lower activity in the linear regime, whereas the extent of the activation becomes greater in the build‐up regime. The origin of these kinetic behaviors is studied using scanning electron microscopy (SEM) for catalyst/polymer particles and cross‐fractionation analyses for polymer structures. It is found that the kinetic transition mainly arises from the fragmentation of the catalyst particles and resultant increase in the active site concentration. The fragmentation manner strongly depends on the alkylaluminum concentration, which affects not only the amount, but also the placement of initial polymer formation. The nature of the active sites varies as a result of an aging effect with alkylaluminum: their stereospecificity, propagation rate constant, and tolerance for chain transfer reaction increase as the polymerization progresses.

High-performance water-soluble polymers have a wide range of applications from engineering materials to biomedical plastics. This article discusses the synthesis of water-soluble polyimide from bio-based monomers.

New soluble biopolyimides were prepared from a diamine derived from an exotic amino acid (4-aminocinnamic acid) with several kinds of tetracarboxylic dianhydride. The biopolyimide molecular structural flexibility was tailored by modifying the tetracarboxylic dianhydride moiety. The obtained polyimides were soluble in various solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, and even tetrahydrofuran. It was observed that the biopolyimide solubility was greatly dependent upon the structural flexibility (torsion energy). Flexible structure facilitated greater solubility. The synthesized biopolyimides were largely amorphous and had number-average molecular weight (Mn) in the range (5–8) × 105. The glass transition temperatures (Tg) of the polymers ranged from 259–294 °C. These polymers exhibited good thermal stability without significant weight loss up to 410 °C. The temperatures at 10% weight loss (Td10) for synthesized biopolyimide ranged from 375–397 °C.

Biopolyamide structure and their silica hybrids performances were studied. Biopolyamide with inability to interact with silanol during sol–gel condensation for silica formation showed superior thermo-mechanical, optical and electrical properties.

Mellophanic dianhydride which is aromatic tetracarboxylic dianhydride monomer for synthesis of polyimide, were derived from maleic anhydride and 2,5-dimethylfuran as the bio-derived monomers with the new approach. The obtained mellophanic dianhydride is used to synthesize the fully bio-based poly(amic acid) using 4-aminocinnamic acid dimer as the bio-based aromatic diamine monomer. For controlling the solubility of polyimide, thermal or chemical imidizations are carried out by using stepwise heating method or acetic anhydride/pyridine treatment, respectively. Thermally imidized polyimides show low solubility for organic solvent, however, chemically-imidized polyimide show good solubility for N-methyl-2-pylloridione, dimethylsulfoxide, and N,N-dimethylformamide. In addition, all the obtained polymers show high heat resistance properties, 10 % decomposed temperature (T d10), of poly(amic acid) is 331 °C, while T d10 of polyimides are 389 °C regardless of imidization processes. Thus, fully bio-based polyimides having high thermostability is developed for the first time.

In order to improve the ethylene polymerization activity and branching ability of Phillips catalysts, various bimetallic catalysts were synthesized on the basis of co‐impregnation of chromium and second metal salts. The activity and branching ability of the catalysts were enhanced by the introduction of zirconium, zinc, and vanadium, while deteriorated by the introduction of molybdenum and tungsten. On the other hand, the structure of metal salt precursors did not greatly affect the catalytic performances. X‐ray photoelectron spectroscopy (XPS) clarified a tendency that second metal with lower electronegativity decreased the electron density on chromium species, resulting in higher polymerization activity of the bimetallic catalysts plausibly due to enhanced ethylene activation. On the other hand, the branching ability of the catalyst improved as the catalyst activity increased due to more facile formation of α‐olefin co‐monomer.

In this work, the effect of long-chain branching (LCB) on the tensile properties of sulfur-cured, unfilled, polypentenamer rubber (PPR) was investigated. Branched PPR, prepared by ring-opening metathesis copolymerization of cyclopentene (CP) and dicyclopentadiene (DCPD), showed improved mechanical strength, demonstrating more than 3 times higher tensile stress at 500% strain compared to its linear counterpart (a homopolymer of CP). In situ wide-angle X-ray scattering showed that branching units caused significant changes in the strain-induced crystallization (SIC). At low temperatures, linear PPR underwent rapid SIC after a critical stretch was reached, while branched PPR crystallized more slowly. However, SIC is not the cause of the enhanced mechanical strength. Elevated temperature experiments confirmed that even in the absence of SIC, LCB PPR exhibits a stiffer stress–strain response. We propose that the stiffer behavior of branched PPR is caused by a reduction in the chain mobility. The origins of reduced chain mobility are likely from topological constraints imposed by the LCB architecture and also from an unintended nanofiller effect created by microphase separation of DCPD-rich domains. The work described here is the initial investigation of adding branching units to PPR to improve the elastomer performance.