Yoshio Shibasaki

Effects of molecular arrangement on polymerization reactions in Langmuir-Blodgett films

Abstract Polycondensation of long-chain esters of α-amino acids and γ-ray-initiated polymerization of long-chain alkyl acrylate were investigated in Langmuir-Blodgett films, in order to clarify the effect of molecular arrangement on the reaction rates and the structure of the products. Multilayers of the long-chain monomers were built up on CaF 2 plates and the polymerization processes were followed by monitoring intensity changes in characteristic bands in the IR spectra. It was found that a regular arrangement with some rotational freedom of the monomer molecules in the layered structure accelerates markedly the polymerization reactions. Mechanisms for two-dimensional polymerization together with the conformations or configurations of the resultant macromolecules are also discussed.

Polymerizabilities of amphiphilic monomers with controlled arrangements in Langmuir-Blodgett films☆

Abstract Polymerization of amphiphilic monomer Langmuir-Blodgett (LB) films, such as long-chain derivatives of α-amino acids and diynoic, trienoic and acrylic acids, was studied. Multilayers of these monomers were prepared on CaF2 or quartz plates by the LB method under various conditions, and polymerization processes were followed by IR and UV spectroscopy. The polycondensation of dioctadecyl- L - glutamate proceeded easily in LB films at ordinary temperatures below the melting point without any initiation. All-trans- and 9-cis-9,11,13-octadecatrienoic acids polymerized very rapidly in LB films on UV irradiation. Photopolymerization in LB films of 10,12-tricosadiynoic acid was influenced by the deposition modes and annealing, and that of octadecyl acrylate was accelerated by the addition of the long- chain vinyl ether. In any case, polymerization reactions are markedly enhanced by a well-controlled arrangement of the monomer molecules in the LB films.

Polycondensation of Long-Chain Esters of α-Amino Acids in Monolayers at Air/Water Interface and in Multilayers on Solid Surface

Abstract Polycondensations of long-chain esters of glycine and alanine in the monolayers spread at air/water interface and in the multilayers deposited on solid surface have been investigated by surface viscosity and IR spectra. These compounds form stable monolayers on neutral and alkaline subphases. The polycondensation can occur rather quickly in the monolayers at room temperature without any catalyst or initiator. The polymerization rate is markedly influenced by the area per molecule and the maximum polymerizability is obtained at the area somewhat larger than the condensed region. Furthermore, polymerizability in the multilayer prepared by Blodgetts technique is superior to those in the bulk powder at the same temperature and in the molten state at higher temperature. These results lead to the conclusion that the polycondensation is accelerated by the regular arrangement of the monomer molecules at the interface, where the functional groups are concentrated and situated most effectively for the rea...

Molecular arrangement and polymerizability of amino acid derivatives and dienoic acid in Langmuir-Blodgett films

Abstract For the purpose of elucidating the effect of molecular arrangement on the reaction rate and the structure of the resulting polymers, two types of polymerization, i.e. polycondensation of long-chain esters of α-amino acids and photopolymerization of long-chain dienoic acid, were investigated in Langmuir-Blodgett (LB) films. Monolayer assemblies with various modes of packing or arrangement of the monomer molecules were built up and the polymerization processes were followed by monitoring the intensity changes of characteristics bands in the IR and UV spectra. It was found that polymerization reactions of both condensation and addition are markedly accelerated when the monomer molecules are organized in LB films. Furthermore, it is suggested that poly-amino acids or poly-dienoic acid with different conformations or configurations can be obtained by controlling the molecular arrangement with the LB technique.

Polymorphism of Acrylic and Methacrylic Acid Esters Containing Long Fluorocarbon Chains and Their Polymerizability

The molecular aggregation of acrylic and methacrylic acid esters containing long-fluorocarbon chains: 2-(perfluoroalkyl)ethyl acrylate (FFnEA) and 2-(perfluoroalkyl)ethyl methacrylate (FFnEMA) (F(CF2)nCH2CH2OCOC(X)=CH2, where X=H, CH3 and n=6, 8, 10) was investigated by differential scanning calorimetry (DSC) and temperature controlled X-ray powder diffraction measurement. These compounds exhibited some characteristic polymorphic behaviors depending on the length of fluorocarbon chain and the α-position methyl group. The solid-state polymerization by γ-ray irradiation was studied for these compounds in the various crystal forms. In the solid-state polymerization, highest polymerizability was observed in the crystal form that exists in the highest temperature region for each compound.

Mechanisms of thermal degradation of polystyrene, polymethacrylonitrile, and their copolymers on flash pyrolysis

The mechanism of thermal degradation of homopolymers of styrene (St) and methacrylonitrile (MAN) and their copolymers was investigated theoretically and experimentally by the pyrolysis gas chromatography using a Curie-point pyrolyzer. Poly(St-co-MAN)s generate dimers and trimers as well as monomers by flash pyrolysis. Parameter α was proposed to account for the competition between the back-biting reaction and depolymerization. The back-biting parameter α is defined as the ratio of rate constants, α = k bb /k dp , where k bb is the rate constant for the back-biting reaction and k dp is that for depolymerization. The back-biting process is followed by β-scission, where dimer and trimer are generated, and directly correlated with the C-H bond dissociation energies in the polymer chain. Using the back-biting parameter α, where 1/α is equal to the zip length n in depolymerization, the boundary effect for the difference of monomer yields from the homopolymers of St and MAN and their copolymers is well explained. The calculated values of boundary effect parameters, β St and β MAN , agreed well with the experimental results. It was found that thermal degradation mechanisms of homo- and copolymers of vinyl compounds can be analyzed comprehensively using the back-biting parameter α and the boundary effect parameter β.

DSC and X-ray studies on side-chain crystallization of comb-like polymers

Thermal properties of acrylate and methacrylate monomers containing long-fluorocarbon chains (H(CF2)nCH2OCOCH=CH2, (FnA) and H(CF2)nCH2OCOC(CH3)=CH2, (FnMA), wheren=6, 8, 10) and their comb-like polymers have been investigated by differential scanning calorimeter (DSC) and X-ray diffraction. The comb-like polymers (PF10A and PF10MA) with sufficiently long-fluorocarbon chains showed a simple melting and crystallizing behavior. For the fusion of PF10A in 1st heating, enthalpy change δHf was 18 kJ mol−1 and entropy change δSf was 45 J K−1 mol−1, while for PF10MA the values δHf and δSf were 5.3 kJ mol−1 and 14 J K−1 mol−1, respectively. Melted PF8A crystallized slowly, whereas PF8MA with same fluorocarbon chain and also both of PF6A and PF6MA with shorter fluorocarbon chains can hardly crystallize by the aggregation of side-chains. Effects of the length of side-chain and the flexibility of main chain on the side-chain crystallization of comb-like polymers are clear. Crystallization process of the methacrylate monomers was sensitively affected by the scanning rate of DSC measurement and the length of fluorocarbon chains.

Spontaneous formation of polypeptides in the interfacial thin films of amphiphilic amino acid esters: acceleration of the polycondensation and control of the structure of resultant polymers

For the purpose of elucidating the effects of molecular arrangements on the reaction rates and the structure of products, polycondensation of long-chain esters of alpha-amino acids in the monolayer on the water surface and the LB multilayers deposited on CaF2 plates were investigated by monitoring changes of the IR spectra. Spontaneous formation of the polypeptides occurs in the mono- and multilayers at room temperature without any catalyst. The rates of polycondensation in the monolayers are markedly influenced by the degree of molecular packing. Maximum polymerizability is obtained in the vicinity of the transition region from expanded to condensed films. The rates of polycondensation in the LB films are much higher than those in the bulk solids and the molten states. The polycondensation seems to be accelerated by regular arrangements of the monomer molecules in the LB films, where the functional groups are concentrated and situated more effectively for the reaction than in the bulk states. However, the polycondensation rates in the LB films are considerably slower when compared with those in the monolayers on the water surface kept at the optimum area or surface pressure, because the molecules in the LB films deposited under high compression are packed more closely than the optimum condition. Thus, suitably close packing of the monomer molecules, retaining a particular orientation together with some conformational freedom in the monolayer, is most favorable for the polycondensation. Two probable mechanisms for the polycondensation in the Y-type multilayers have been proposed. In the assembly of head-to-head double layers of the monomer molecules, the interlayer reaction propagates by sewing up the functional groups facing each other in the adjacent layers, and the polypeptide of a helical structure or random coil can be obtained. In contrast, for the alternating assembly of the amino acid ester and non-polymerizable octadecyl acetate, the polycondensation should proceed only in each single layer (intralayer reaction) and the polypeptide of the extended beta-form can be formed. In the case of dioctadecyl glutamate LB films, as well as the monolayer on water, the resultant polypeptide is the comb-like polymer with unreacted long-alkyl ester groups as side chains and abundant in the beta-form, indicating the dominant intralayer reaction. On the other hand, in the Y-type multilayer of the equimolar mixture of dioctadecyl glutamate (with two ester groups) and octadecyl ester of lysine (with two amino groups), both of the intra- and interlayer reactions occur effectively, resulting in a two-dimensional network structure of the polypeptide. In conclusion, not only the rate of polycondensation but also the higher-order structure of the resultant polypeptides can be controlled by organized arrangements of the monomer molecules in the interfacial thin films.

Control of polymerization reactions and polymer structures through the molecular orientation of amphiphilic monomers in Langmuir-Blodgett films

Abstract The effect of molecular orientation on the polymerization of various amphiphilic monomers in Langmuir-Blodgett (LB) films was studied. Multilayers of amphiphilic monomers were deposited on CaF2 or quartz plates and polymerization processes were followed by IR and UV spectroscopies. The polycondensation of octadecyl- L -lysine ester, dioctadecyl- L -glutamate and their mixtures proceeded easily in LB films at ordinary temperatures without initiator. Photopolymerization of tricosa-10,12-diynoic acid in LB films was remarkably influenced by conditions of monolayer formation and annealing of the LB films. Photopolymerization of vinyl stearate was accelerated by addition of octadecyl acrylate. Polymerization reactions of any type are markedly enhanced and the structures of the resultant polymers can be controlled through the molecular orientation and arrangement of the monomers in the LB films.

Study on microstructures of mixed monolayers of poly (octadecylacrylate) and octadecanol in relation to the retardation of water evaporation

Abstract In a series of studies on retardation of water evaporation by the binary mixed monolayer of poly (vinyl long-chain ester) and octadecanol (OA), microstructures obtained by a Brewster angle microscopy (BAM) and atomic force microscopy (AFM) images have been investigated with varying the composition of mixed monolayer of poly (octadecylacrylate) (POA) and OA. The mixed monolayer of POA/OA=1:3–1:4 exhibits considerably effective resistance to water evaporation at 20–40 mN/m, which is reflected in the condensation effect by mixing on the π – A isotherms. From the BAM image of each monolayer at zero pressure the rather heterogeneous film was obtained for the single component and the homogeneity of the monolayer was apparently improved by their mixing. The flattest BAM image could be obtained for the mixed monolayer of POA/OA=1:3 in the submillimeter scale. This result has good correspondance to the retardation effect of the mixed monolayer on water evaporation. On the other hand, for the AFM image of POA film some defects with depth of about 1.9 nm were observed and small ones still remained by adding OA in the nanometer scale.