The lamella thickness distribution (LTD) plays a critical role for the mechanical properties of linear low-density polyethylene (L-LDPE). For example, a narrower LTD gives a higher impact strength. LTD is predominantly governed by the intermolecular chemical composition distribution (CCD) as shown typically for L-LDPE prepared with heterogeneous catalyst systems. For L-LDPEs with a narrow CCD, the intrachain heterogeneity, i.e., the ethylene sequence length distribution becomes significant and thus results in a broadened LTD. Short chain branching (SCB) affects LTD through their inclusion in lamellar crystals, more inclusions broaden LTD. The effects of sequence length heterogeneity and SCB bulkiness on LTD were clearly revealed in alkyl-branched acyclic diene metathesis (ADMET) polyethylene that contains pristine microstructures free from inter and intrachain heterogeneity. ADMET-PE shows a very narrow LTD that is independent from the kind of SCB. The average lamella thickness and the crystal polymorph correspond to the CH₂ spacer length and the kind of SCB.

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Strain-induced crystallization of cross-linked rubber significantly affects its strength and mechanical properties. To date, theories on the thermodynamic equilibrium of strain-induced crystallization have been proposed. However, the effects of the crosslinking density from these theories are not consistent with the experimental results. Recent experiments using synchrotron radiation led to a better temporal and spatial resolution. Time constants of strain-induced crystallization could be estimated and a quantitative discussion about the relationship between strain and crystallization rate became possible. At the same time, the stress relaxation of cross-linked rubber at a fixed length was found to be mainly due to strain-induced crystallization. These new experimental results are also inconsistent with the thermodynamic theories. In order to explain the experimentally obtained data of the strain-induced crystallization, a heterogeneity of the network structure must be considered. As a result of the recent studies, a more detailed understanding of the reinforcing effect by strain-induce crystallization is becoming possible.

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The micro-phase separated structures of ABA triblock copolymers comprising flexible amorphous poly(methacrylate) (PMA, A block) and semiflexible liquid crystalline (LC) polyester (B block) with amorphous block volume fractions (ϕ_am) ranging from 0.2 to 0.8 were investigated. For ϕ_am < 0.52, block copolymers formed lamellar microdomains. The LC segments extended perpendicular to the interface and formed smectic layers parallel to the lamellae. The segments folded within the lamellae, whereas the amorphous segments had dimensions similar to those of in amorphous block copolymers. When ϕ_am > 0.68, the LC lamellae divided into cubes, transforming into spheres in the PMA matrix. Our results demonstrate that flexible-semiflexible-flexible block copolymers can change their morphology characteristically by the contour length and flexibility of the semiflexible segment in addition to other factors known for flexible copolymers.

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The crystal structure analysis of various polymer substances has been reviewed on the basis of wide-angle high-energy X-ray and neutron diffraction data. The progress in structural analytical techniques of polymer crystals have been reviewed at first. The structural models proposed so far were reinvestigated and new models have been proposed for various kinds of polymer crystals including polyethylene, poly(vinyl alcohol), poly(lactic acid) and its stereocomplex etc. The hydrogen atomic positions were also clarified by the quantitative analysis of wide-angle neutron diffraction data, from which the physical properties of polymer crystals have been evaluated theoretically. The bonded electron density distribution has been estimated for a polydiacetylene single crystal on the basis of the so-called X-N method or by the combination of structural information derived from X-ray and neutron diffraction data analysis. Some comments have been added about future developments in the field of structure-property relationship determination.

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Microbial polyesters, which are bio-synthesized from renewable carbon recourses such as sugars and plant oils, are biodegradable in the natural environment. For this reason, these polymers are of interest for solving environment and resource problems. However, they have not been put into practical use due to their brittleness, but in recent year, the physical properties could be improved. This report introduces a new drawing method, the development of materials by the bio-synthesis of ultra-high-molecular-weight microbial polyesters and their blends. Furthermore we report on the relationship between crystal structure, highly order structure and physical properties of those improved materials and their enzymatic degradation behavior.

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Syndiotactic polystyrene (sPS) is a relatively new commodity polymer, which exhibits a variety of solid states. One of the important characteristics of sPS is the formation of co-crystals, where a variety of chemical compounds can be stored as guests in the cavities between sPS helices of (T₂G₂)₂ conformation. The guest molecule can be exchanged with other chemical compound by exposing a sPS co-crystal film to a vapor, a liquid or a solution of the new guest molecule. In particular, the addition of an additive to a liquid of the new guest molecule promotes the guest exchange process and facilitates the incorporation of bulky molecules into the crystalline region of sPS co-crystals. It has been reported that a variety of compounds including functional molecules can be incorporated into the sPS lattice by using this additive assisted guest exchange phenomenon. In this paper, we show at first that polyethylene glycol dimethyl ethers, which far exceed previous guest molecules in molecular weight, can be incorporated into the crystalline region of sPS co-crystals. Next, we review the results of ATR FT-IR spectroscopy and small angle neutron scattering experiments of the guest exchange process.

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The morphology of ice crystals in supercooled aqueous solutions of antifreeze glycoprotein (AFGP) in the range from −0.01 to −1.0°C was investigated by varying the protein concentration from 0 to 1.0 mg/mL. At around −0.4°C, we observed a new morphology of ice crystal at 1 mg/mL AFGP concentration. The ice crystal had multiple plates that grew radially in a plane. The tip of each plate crystal showed a faceted structure. Furthermore, at the same concentration, a fernlike stellar dendritic ice crystal, which looks like naturally formed snow crystals at around −14°C, was observed at −1.0°C. The ratio of the growth rates between prism planes in the presence of AFGP at −1.0°C may be similar to that achieved at around −14°C in natural atmospheric conditions.

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In order to clarify the effects of multiple hydrogen bonds between chain ends on the crystal growth of polymers, we studied the growth rate of crystal G of polyethylene (PE) having amino groups and thymine units in the terminal (PE-Thym) and polydioxanone having hydroxy groups and thymine units in the terminal (PDX-Thym) from the melt as a function of the degree of supercooling ΔT by means of polarizing optical microscope, DSC and WAXS. PE-Thym and PDX-Thym have multiple hydrogen bonds between their terminals. We also prepared PE having amino and hydroxy groups in the terminal (PE-OH) and PDX having carboxy and hydroxy groups in the terminal (PDX-OH) as reference samples. Those show weak single hydrogen bond between their terminals. Number average molecular weights M_n of PE-Thym and PE-OH are almost the same (M_n = ca. 2000). M_n of PDX-Thym and PDX-OH are 3000 and 5600, respectively. G of all the samples obeyed the equation, G = G₀exp(–B/ΔT). The exponent B for PE-Thym and PDX-Thym is almost the same as for PE-OH and PDX-OH. Since B is proportional to the surface free energy of the end surface of the nucleus, this indicates that the regularity of folding at the surface is also the same. On the other hand, G₀ of PE-Thym and PDX-Thym is much less than that of PE-OH and PDX-OH. We speculate that the reeling motion from the melt to the nucleus during crystal growth is suppressed due to the formation of a dynamic multiple-hydrogen-bond network between chain ends in the melt. Moreover, in order to shield the multiple hydrogen bonds in the terminal, we studied the ΔT dependence of G for PDX-Thym with added adenine. Compared to PDX-Thym without added adenine, we found that the ΔT dependence of G changed. This indicates that the influence of hydrogen bonds on crystal growth is closely related with the regime of crystal growth.

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Changes in the density fluctuations of polyethylene on the submicron scale under uniaxial stretch were investigated by means of ultra-small angle X-ray scattering (USAXS) as a function of strain. Small angle X-ray scattering (SAXS) and wide angle X-ray scattering (WAXS) were also used in order to get information on a very wide spatial scale from 0.1 nm to 1000 nm. On the submicron scale, heterogeneous density fluctuations developed with strain. The development of the fluctuations was anisotropic; the fluctuations along the stretch direction were larger than along the perpendicular direction. The former fluctuations developed in two steps; the development before the yield point was larger than after the yield point. On the other hand, the lamella structure was deformed and the crystal lattice was oriented in proportion to strain.

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In the present study, we investigate the micron-scale inhomogeneous distribution of silica nanoparticles with X-ray near-field scattering. This technique allows us to measure structures of soft matters on a large size scale that is complementary to conventional ultra-small-angle X-ray scattering and/or X-ray imaging. We applied the technique to the observation of the anisotropic structural distribution of silica aggregates in uniaxially stretched rubber. The scattering images show anisotropic butterfly patterns that correspond to the inhomogeneous density distribution of silica aggregates. The spatial distribution of the inhomogeneity in the stretched rubber cab also be determined by this technique.

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Polystyrene-b-poly(2-vinylpyridine) (S2VP) incorporating FeCl₃(III) thin films were prepared by spin-coating on silicon wafers from tetrahydrofran (THF) solution. Spherical domains (micelles) formed in the solution by addition of FeCl₃(III) which induced cross-linking through a coordinate bond between iron ion and nitrogen in the vinyl pyridine units. To study the micro-phase separated structure in the thin films, atomic force microscopy and grazing-incidence small angle X-ray scattering were used. Interestingly, addition of FeCl₃(III) to S2VP induced orientation of cylindrical microdomains perpendicular to the silicon substrate. In contrast, the perpendicular orientation did not occur in the S2VP thin film without iron ions. The key to the vertically oriented cylinders in the film is a phase-transition from micelles to cylinders along the THF solvent evaporation direction during casting and THF penetration direction during annealing.

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We performed small-angle and wide-angle X-ray scattering (SAXS and WAXS) measurements on poly(ethylene terephthalate) (PET) films that were uniaxially rolled above the glass transition temperature. A smectic structure was observed for films drawn at 90°C, while a crystalline was grown for films drawn at 100°C. We found characteristic SAXS patterns for films with a draw ratio of more than 300%: a two-point pattern observed in through views, and four-point pattern observed in edge views. For the case of higher draw ratios, the peak position of the two-point pattern shifts to a higher scattering angle with an increase of peak intensity. Another characteristic pattern is the X-shaped streak, which stand out in particular for the edge view patterns. The four-point pattern was overlapped on the X-shaped streak for draw ratios of over 300%.

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The gas permeation and diffusion properties of drawn and undrawn membranes of poly(4-methyl-1-pentene) (PMP) membranes were investigated in relation to the orientation of the crystal phase. From the results of infrared dichroism and X-ray diffraction, we conclude that the c-axis of PMP crystals are uniaxially oriented in the drawing direction. The permeation coefficients of these drawn membranes for relatively small gas molecules were smaller than those of the undrawn membranes with randomly oriented crystals. On the other hand, the permeation of large gas molecules is not effected by the orientation of the crystals. Furthermore, we found a diffusion anisotropy of the PMP crystals when investigating the diffusion behavior of the methane in PMP membranes by pulsed field gradient ¹H NMR.

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The crystalline hard segment models of segmented polyurethane elastomers are made of 4,4′-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD). Here we investigate the crystalline behavior of polyurethane that in addition contain 1,1,1-trimethylol propane (TMP), poly(oxytetramethylene) glycol (PTMG), and polyethylene glycol (PEG). The melting points (T_m) of crystallized MDI-BD units decreased with increasing TMP contents and increased with increasing PTMG contents, respectively. A decrease in molecular weight of PTMG and incorporation of PEG decreased T_m. These results indicate that incorporation of a third component would cause to form the well-ordered crystal being closed to equilibrium state.

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