CaCO₃ mineralization in polymer composites with cellulose nanocrystals providing a chiral nematic mesomorphic structure

CaCO₃ mineralization was carried out using cellulose nanocrystal (CNC)/polymer composites wherein a chiral nematic structure of CNC assembly was immobilized in advance via a polymerization process of the precursory aqueous CNC/vinyl monomer lyotropics (7–11 wt% CNC in feed). Two series of polymer composites were prepared: CNC/poly(2-hydroxyethyl methacrylate) (PHEMA) and CNC/poly(2-hydroxyethyl methacrylate-co-acrylic acid) (P(HEMA-co-AA), HEMA:AA = 95:5–70:30 in mol). The mineralization was allowed to proceed solely by soaking the composite films in a salt solution containing Ca²⁺ and HCO₃− under a low-basic condition (pH ≤ 9). Polymorphism of CaCO3 deposited inside the films was examined by X-ray diffractometry as a function of the soaking time (1–5 day) and also of the matrix composition. In the CNC/PHEMA series, the polymorphic form changed from amorphous calcium carbonate (ACC) (1-day soaking) to metastable crystalline vaterite (3-day soaking) and then to a mixture of vaterite and aragonite (5-day soaking). In the mineralization of the CNC/P(HEMA-co-AA) series, the formation of stable calcite was prominent besides minor appearance of vaterite. It was deduced that the mesofiller CNC and the AA unit in the vinyl polymer, both bearing an anionic group (-SO₃− or -COO−), contributed to capturing Ca²⁺ to facilitate the CaCO₃ deposition in the swollen film matrix. The pre-invested chiral nematic organization was kept in any of the mineralized films (dried); however, the helical pitch was appreciably reduced relative to that observed before the mineralization, attributable to the increase of ionic strength in the CNCs' surroundings accompanied by the wet process. Thermogravimetry showed that the mineralization definitely improved the thermal performance (heat/flame resistance) of the mesomorphic order-retaining CNC/polymer composites

セルロースエステルとビニル共重合体から成るブレンドの相溶性と分子間相互作用に関する比較研究

京都大学0048新制・課程博士博士(農学)甲第19197号農博第2136号新制||農||1034(附属図書館)学位論文||H27||N4943(農学部図書室)32189京都大学大学院農学研究科森林科学専攻(主査)教授 西尾 嘉之, 教授 木村 恒久, 教授 髙野 俊幸学位規則第4条第1項該当Doctor of Agricultural ScienceKyoto UniversityDFA

Insight into miscibility behaviour of cellulose ester blends with N-vinyl pyrrolidone copolymers in terms of viscometric interaction parameters

We previously offered miscibility maps for blend systems of cellulose esters (CEs) including cellulose acetate (CA), propionate (CP), and butyrate (CB) with vinyl copolymers containing an N-vinyl pyrrolidone (VP) unit, i.e., poly(N-vinyl pyrrolidone-[co]-vinyl acetate) [P(VP-[co]-VAc)] and poly(N-vinyl pyrrolidone-[co]-methyl methacrylate) [P(VP-[co]-MMA)]; the maps were constructed based on data of thermal analysis as a function of the degree of ester substitution (DS) of the CE component and the VP fraction in the copolymer component. The blend system using CP among the three CEs imparted the largest region of miscible pairings with the vinyl copolymers, and both of the maps for the CP/P(VP-[co]-VAc) and CP/P(VP-[co]-MMA) systems comprised a "miscibility window" associated with the respective copolymer compositions at high DSs of >2.65. The present work was made to interpret the expansion of the miscible markings for the CP/copolymer systems in comparison with the cases using CA and CB, in terms of a Krigbaum–Wall interaction parameter (μ) obtained by solution viscometry for selective polymer pairs involved in the respective CE/copolymer blends. The results of μ measurements were in good accordance with the earlier miscibility estimations. The assessment of very small negative μ values (i.e., extremely weak repulsion) for CP/PVAc and CP/PMMA combinations and that of considerably larger negative μ values for PVP/PVAc and PVP/PMMA combinations enabled us to give a rational explanation for the CP systems. The strongly repellent character of the two different monomer units constituting the copolymers permits accession of the CP component (DS > 2.65) to them, which would be responsible for the advent of the miscibility window. Further expansion of the window observed when cellulose acetate propionate (CAP) was adopted instead of CP as the CE component was also well explained on the basis of a μ data indicative of additional intramolecular repulsion in the CAP side

Blend miscibility of cellulose propionate with poly(N-vinyl pyrrolidone-co-methyl methacrylate).

The blend miscibility of cellulose propionate (CP) with poly(N-vinyl pyrrolidone-co-methyl methacrylate) (P(VP-co-MMA)) was investigated. The degree of substitution (DS) of CP used ranged from 1.6 to >2.9, and samples for the vinyl polymer component were prepared in a full range of VP:MMA compositions. Through DSC analysis and solid-state (13)C NMR and FT-IR measurements, we revealed that CPs of DS<2.7 were miscible with P(VP-co-MMA)s of VP≥~10mol% on a scale within a few nanometers, in virtue of hydrogen-bonding interactions between CP-hydroxyls and VP-carbonyls. When the DS of CP exceeded 2.7, the miscibility was restricted to the polymer pairs using P(VP-co-MMA)s of VP=ca. 10-40 mol%; the scale of mixing in the blends concerned was somewhat larger (ca. 5-20 nm), however. The appearance of such a "miscibility window" was interpretable as an effect of intramolecular repulsion in the copolymer component. Results of DMA and birefringence measurements indicated that the miscible blending of CP with the vinyl polymer invited synergistic improvements in thermomechanical and optical properties of the respective constituent polymers. Additionally, it was found that the VP:MMA composition range corresponding to the miscibility window was expanded by modification of the CP component into cellulose acetate propionate

Cellulose propionate/poly(N-vinyl pyrrolidone-co-vinyl acetate) blends: dependence of the miscibility on propionyl DS and copolymer composition

Blend miscibility of cellulose propionate (CP) with synthetic copolymers comprising N-vinyl pyrrolidone (VP) and vinyl acetate (VAc) units was examined, and a data map was constructed as a function of the degree of substitution (DS) of CP and the VP fraction in the copolymer component. Results of differential scanning calorimetry and Fourier transform infrared measurements indicated that the pairing of CP/P(VP-co-VAc) formed a miscible or immiscible blend system according to the balance in effectiveness of the following factors: (1) hydrogen bonding between residual hydroxyls of CP and VP carbonyls of P(VP-co-VAc); (2) steric hindrance of propionyl side-groups to the interaction specified in (1); (3) intramolecular repulsion between the two units constituting the vinyl copolymer; and, additionally, (4) structural affinity between two segmental moieties involving the propionyl group and VAc unit, respectively. The factor 3 inducing intercomponent attraction is responsible for the appearance of a so-called "miscibility window" in the miscibility map, and the factor 4 substantially expands the miscible region whole, wider relative to those in the maps for the corresponding blend series based on cellulose acetate and butyrate. In further refined estimation by dynamic mechanical analysis and T_[1ρ]^H quantification in solid-state [13]C NMR, it was found that the miscible blends of hydrogen-bonding type (using CPs of DS 2.7) formed blends exhibiting a somewhat larger size of heterogeneity (ca. 5–20 nm)

Preparation and chiroptical properties of cellulose chlorophenylcarbamate–silica hybrids having a chiral nematic mesomorphic structure

An attempt was made to fabricate optically functional cellulosic–silica hybrid materials wherein a helically ordered mesomorphic structure of the cellulosic component was fixed. Cellulose 3-chlorophenylcarbamate (3Cl-CPC) and cellulose 4-chlorophenylcarbamate (4Cl-CPC) were synthesized by carbanilating reaction of cellulose with 3-chlorophenyl or 4-chlorophenyl isocyanate in a homogeneous solution system. The hydrophobic cellulose derivatives were examined for the solubility and liquid crystallinity in various solvents containing alkoxysilane as a main component. Concentrated (∼40 wt%) solutions of 3Cl-CPC in 3-aminopropyltrimethoxysilane (APTMS) and those of 4Cl-CPC in a mixed solvent of tetramethoxysilane (TMOS)/N, N-dimethylformamide (DMF)/dichloroacetic acid (DCA) formed a chiral nematic mesophase to impart vivid reflection colors. These liquid crystalline solutions were subjected to a sol–gel conversion process of the respective alkoxysilane components in moist air. In the process for the 4Cl-CPC lyotropic system, we utilized a "surface-coating solvent" consisting of TMOS/phenyltrimethoxysilane/DCA to facilitate the sol–gel reaction of TMOS and also to preserve the reflective coloration. Thereby a left-handed chiral nematic hybrid series of 4Cl-CPC–silica was successfully obtained as a monolithic glassy bulk showing iridescent colors. The 3Cl-CPC/APTMS lyotropics were readily converted into a colored solid form without any coating solution, resulting in production of a right-handed chiral nematic series of 3Cl-CPC–silica. Besides investigating the chiroptical characteristics of the liquid crystalline solutions and hybrids, we preliminarily tried separating a racemic compound into two enantiomers by open column chromatography using the cellulosic–silica hybrids as a filler material of the column

Rapid Benzylation of Cellulose in Tetra-n-butylphosphonium Hydroxide Aqueous Solution at Room Temperature

We found a very fast benzylation of cellulose in a tetraalkyl-onium hydroxide solvent system, 47% tetra-n-butylphosphonium hydroxide aqueous solution. Benzyl cellulose (BC) with a degree of substitution (DS) above 2.5 was obtained within 10 min at ambient temperature (20–25 °C) using ∼9 mol equiv of benzyl bromide to the anhydroglucose unit. The highly efficient benzylation proceeded in the transiently stabilized emulsion state of the reaction system, and the product precipitated out as a solid sediment in the liquid medium. At 20 °C, the benzyl DS was 1.92 after 2 min, and reached 2.40 and 2.53 after 5 and 10 min, respectively. The reaction temperature had a negative correlation with the maximum DS in the explored range of 10–50 °C. No significant degradation of the cellulosic main chain was observed for highly substituted BCs (DS > 2.5). The solubility of BC in common organic solvents was also examined for products with various DSs

Development of Lignin-Based Terpolyester Film and Its Application to Separator Material for Electric Double-Layer Capacitor

For new application of technical lignins as separator material for electric double-layer capacitor (EDLC), we tried first to prepare bipolyester film by melt-polycondensation of polyethylene glycol lignin (PEGL) and maleic anhydride. The EDLC assembled with this film, however, showed lower electrochemical performance than the reference EDLC with commercial cellulosic separator. Porous bipolyester film was then prepared and the resulting EDLC exhibited improved specific capacitance, but high intrinsic and charge transfer resistances. Non-porous terpolyester film was prepared next, using polyethylene glycol 500,000 to improve flexibility of the film, which might lower the resistances. This film was flexible enough and provided the resulting EDLC with superior electrochemical performance to the bipolyester film. EDLC with porous terpolyester film was finally prepared and showed the highest electrochemical performance, comparable to the reference EDLC. Porous morphology and flexibility were key factors to fabricate lignin-based self-standing film as separator material for high-performance EDLC