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Comparison of the dielectric relaxation (DR) behaviors of two polar rod-like low-mass molecules (LMs), cyanobiphenyl (CB) and 5-phenyl-2,3′-bipyridine (PBP), in antiplasticized polycarbonate (PC) revealed that rotations around the short and long axes of the LMs appeared from 60 to 125 °C (β region) and from −150 to −50 °C (γ region), respectively. The cooperativity between the local dynamics in PC, measured by dynamic mechanical analysis, and the rotation of the LMs around the short axis was examined based on the relaxation times and activation energies for the LMs (CB and PBP) and PC. The dynamic cooperativity involved the antiplasticization of PC. In contrast, the rotation of the LM (PBP) around its long axis was independent of the local motion in PC, resulting in no contribution to the antiplasticization phenomenon. Adding rod-like low-mass molecules (LMs) increases the elastic modulus of polycarbonate (PC). The anisotropy of the rotational dynamics of rod-like LMs in PC was investigated by dielectric relaxation and dynamic mechanical analysis. Two rotations of the LM around the short and long axes were separately observed at 80 °C and −100 °C, respectively. The rotation of the LM around the short axis was cooperative with the local dynamics of PC and. In contrast, the rotational motion around the long axis was independent of PC motions.

Stretching vibrations of aliphatic C-D bonds at the chain end and midchain site of partially deuterated polystyrene (PS) were determined by Fourier transform infrared (FT-IR) spectroscopy. It was first found that the stretching vibration at the chain end is more rapid compared to that at the midchain site in the glassy bulk state. The difference in the frequencies of the stretching vibrations at the chain end and midchain site changed little even when the PS was dissolved in toluene. Moreover, the DFT vibrational frequency calculations showed that the C-D bonds at the end site intrinsically have higher vibrational frequency because of lower intramolecular interactions at the chain end. From these results, it was concluded that the main origin for the local rapid stretching vibration at the chain end is not intermolecular effects but reduced intramolecular interactions induced by the discontinuity of the repeating unit at the chain end.

We have investigated the relation between the polymer and low-mass molecule (LM) dynamics in antiplasticized polycarbonate (PC). Antiplasticization results in enhancement of the Young’s modulus of polymeric materials by adding LMs. Comparison of the dynamic mechanical properties and dielectric relaxation behavior suggests that the LMs are immobile below room temperature (~ 25 ºC) and mobile above room temperature. The LM dynamics shows a similar trend to the local chain motion of PC, indicating the dynamical relation between the two components. Additionally, we investigated the effect of the LM size on antiplasticization and the local chain motion of PC by using alkyl cyano-biphenyl with various carbon numbers and 4-pentyl-4′-cyanoterphenyl. The LM size does not affect the degree of modulus enhancement of PC at the room temperature. However, mechanical relaxation of the local chain motion of PC shows wider temperature dependence for shorter LM size. The activation energy of molecular motion decreases with decreasing LM size, indicating that restriction of the local chain motion of PC and the LMs becomes weaker for smaller LM size.

Birefringence and its wavelength dependence are important properties for optical applications, such as liquid crystal displays and pick-up lenses. Cellulose esters, which are eco-friendly materials from biomass resources, have been used in optical materials due to their transparency and heat resistance. This review summarized our recent works on birefringence control of cellulose esters by substitution of multiple ester groups, addition of low-mass molecules, and formation of a porous structure. Cellulose acetate propionate (CAP), which has acetyl and propionyl groups in a pyranose unit, exhibited positive birefringence with extraordinary wavelength dispersion owing to contributions from its two esters, while cellulose triacetate (CTA) showed negative birefringence with ordinary dispersion. Moreover, the effect of substitution sites (C-2, C-3, and C-6) on birefringence and its wavelength dependence was investigated by comparing birefringence data of CTA and xylan acetate. The addition of low-mass molecules improved the value of birefringence due to the intermolecular orientation correlation with the matrix cellulose esters. The anisotropic porous structure in CTA films, which was prepared by thermoinduced phase separation, generated extraordinary wavelength dispersion of birefringence. We successfully controlled birefringence and its wavelength dispersion of cellulose esters by choosing different ester substitution groups and sites, controlling the orientation of the crystal, adding low-mass molecules, and forming microscale porous structures. The substitution of two ester groups could provide extraordinary wavelength dispersion of birefringence, which is important for wide-range retardation films. The low-mass additives enhance birefringence values due to the intermolecular orientation correlation with matrix cellulose esters. The anisotropic microporous structure produced by thermoinduced phase separation generates form birefringence, which improves the total birefringence of cellulose esters.

The effect of acetyl substitution on the optical properties of cellulose acetate (CA) was investigated in the present study, because a strong demand for advanced retardation films increases greatly these days. The hot-stretched films with high acetyl substitution had negative orientation birefringence, whereas those with low acetyl substitution had positive orientation birefringence with extraordinary wavelength dispersion. It should be noted that orientation birefringence hardly relaxed even after cessation of hot-stretching. The slow relaxation of crystal orientation was responsible for the anomalous optical anisotropy, as confirmed by two-dimensional X-ray diffraction. Moreover, the slow relaxation of orientation birefringence would greatly benefit the preparation of CA optical retardation films by hot-stretching, because it would simplify the precise control of retardation. The stress-optical coefficient in the glassy state was also evaluated, and was found to decrease with the degree of acetyl substitution. This is an attractive property for optical film applications.

Toughness enhancement of amorphous glassy polymers is required to expand the application range of thermoplastic polymers. This report describes the implantation of ductile nature into poly(methyl methacrylate) (PMMA) resins utilizing a graft architecture with a flexible polyester main chain, which was synthesized via atom transfer radical polymerization (ATRP) with a graft-from approach using a polyester macroinitiator bearing multiple bromo side groups. A comparison with a PMMA homopolymer and a blend PMMA containing a plasticizer revealed that the graft-type PMMA showed much higher elongation without sacrificing the modulus. The ductile nature of the graft-type PMMA was analyzed according to X-ray scattering, scanning electron microscopy observation, and rheological measurement. In the last section, effects of the length of both main chain and graft chain on the tensile properties were investigated.

We controlled the optical anisotropy of a solution-cast film composed of cellulose triacetate (CTA) by adding ferrocene. Owing to the molecular orientation in the film plane of solution-cast films, which results from the normal stress applied during the solvent evaporation process, the average refractive index is usually higher in the plane of the film than in the thickness direction. We found that the addition of ferrocene, which is miscible with CTA, reduced the optical anisotropy by nematic interaction; i.e., ferrocene molecules are forcibly embedded into the film plane accompanying the CTA chains. Because the direction of anisotropic polarizability of ferrocene is perpendicular to the long axis of the molecule, the refractive index in the thickness direction is reduced. Furthermore, the stress-optical coefficient in the glassy state is reduced by the addition of ferrocene.

We have investigated the effect of antiplasticization on the stress-optical behavior of polycarbonate (PC) containing terphenyls (tPh) and di(2-ethylhexyl)adipate (DEHA). Addition of the three tPhs (p-, o-, and m-tPh) and DEHA at contents of 5–10 wt % increases the tensile storage modulus (E') of PC owing to the antiplasticization effect. In particular, p-tPh increases E' more than the other additives, suggesting that the rod-like shape matches the free volume of PC in the glassy state. The three tPh isomers improve the glassy birefringence of PC while DEHA does not change the glassy birefringence, which corresponds to the polarizability anisotropy. The stress-optical coefficient, a ratio of stress and birefringence, of PC decreases with increasing additive content in order of p-tPh ≫ o-tPh > m-tPh = DEHA. This result is agreement with a restricted rotational motion of additive molecule in PC, which is observed in dynamic mechanical and birefringence data. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017

Cross-linked poly(ethyl acrylate-co-methyl methacrylate) (P(EA-MMA)) nanoparticles were prepared by soap-free emulsion polymerization. Size of the isolated nanoparticles in various organic solvents was largely swollen when the solubility parameter of the solvent was similar to that for P(EA-MMA). Well-ordered colloidal crystal assembly film of the P(EA-MMA) nanoparticle was prepared by drying the as-prepared aqueous suspension. The transparent and colorless film exhibited structural color when it was swollen in the organic solvent. Wavelength of the structural color revealed linear relationship with the size of the isolated nanoparticle in the same solvent. This solvent-responsive color-changing behavior explained that the solvent swelling of the nanoparticle increased the repeating distance of the colloidal crystal and the wavelength of the reflected light from the ordered structure. These results suggest that the structural color of the swollen film can be tuned by the solvent quality for P(EA-MMA).

We investigated wavelength dependence of birefringence (Δn) for cellulose acetate propionate (CAP) films stretched at various draw ratios (DRs) and strain rates (SRs), by comparing the result of cellulose triacetate (CTA). CAP exhibited an extraordinary wavelength dispersion of Δn although CTA showed an ordinary dispersion, indicating that Δn of CAP is determined by acetyl and propionyl groups. The extraordinary dispersion for CAP became stronger at larger DR and higher SR. The thermal analysis data suggested that the hot-stretching induces the crystallization of CAP and the crystal size increases with increasing DR and SR. Furthermore, two-dimensional X-ray diffraction pattern of CAP exhibited the orientation of the induced crystal as well as that of CTA, which is one of semi-crystalline polymers. These results mean that the acetyl orientation in CAP becomes stronger than the propionyl orientation. This conclusion is reasonable because acetyl group is more tightly confined to a pyranose ring than propionyl.

The impact of different mixing methods on flow instability in capillary extrusion was examined using binary mixtures of linear low-density polyethylene with different molecular weights. The polymers were blended using a single-screw extruder, a twin-screw extruder, and a twin-screw mixer. The onset of flow instability changed depending on the mixing method used, even though their linear viscoelastic properties were almost identical. The mixtures that were subjected to mixing methods with weak mixing capability exhibit sharkskin failure even at low shear stress and low values of the maximum draw ratio without rupture in the molten state. The results suggested that mechanically weak points were present, which led to cohesive failure at the strand surface following abrupt stretching at the die exit (i.e., sharkskin failure). In contrast, the mixture that was subjected to thorough mixing exhibited smooth surface at high shear stress and a large maximum draw ratio.

The effect of ion-dipole interaction between lithium cations and oxygen atoms in poly(methyl methacrylate) (PMMA), which leads to the great enhancement of glass transition temperature (Tg), on the linear viscoelastic properties is studied using binary blends of PMMA and lithium trifluoromethanesulfonate (LiCF3SO3). The strong interaction at low temperature leads to the high modulus in the glassy region even near Tg. The interaction becomes weak as increasing the temperature. Consequently, the rheological terminal region is clearly detected without a marked enhancement of steady-state compliance, although the zero-shear viscosity increases by the LiCF3SO3 addition. The result indicates that the crosslinking due to the ion-dipole interaction has a lifetime that decides the longest relaxation time. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2388–2394

Interphase transfer of a coumarone-indene tackifier between natural rubber (NR) and poly(isobutylene) (PIB) was studied. The laminated sheets composed of NR with the tackifier and PIB with the tackifier were annealed at various temperatures to promote the interphase transfer of the tackifier. After separating the post-annealing sheets, the infrared spectra were measured to evaluate the tackifier content in each rubber sheet. It was found that a large amount of the tackifier resided in PIB after annealing at -20 °C, whereas the tackifier moved to NR at 40 °C. Consequently, the NR sheet exhibited lower glass transition temperature T_g after annealing at -20 °C and higher T_g when annealed at 40 °C. The differential scanning calorimetry measurements revealed that the crystallization of NR was responsible for the tackifier transfer. This phenomenon should be noted of interest because the matrix of their blend shows low T_g at low ambient temperature and high T_g at high temperature when NR is the matrix of the blend.

The effect of crystallization on the drawdown force, i.e., the force needed to stretch a molten polymer uniaxially, was studied using conventional polyethylene samples. It was found that the drawdown force of high-density polyethylene (HDPE) increases with increasing the die length. This is attributed to the rapid crystallization owing to the low density of entanglement couplings after passing through a long die. On the contrary, the die length has no/little influence on the drawdown force of linear low-density polyethylene (LLDPE), indicating that the molecular orientation applied in a long die is almost relaxed prior to the crystallization. Even for LLDPE, however, the drawdown force becomes sensitive to the die length by the addition of a small amount of HDPE, because the crystallization process is accelerated.

Poly(ethylene-co-vinyl acetate) with 42 wt% of vinyl acetate shows autonomic self-healing at room temperature without macroscopic flow. Intermolecular diffusion of amorphous chains through the jointed boundary, which occurs because of the large amount of amorphous chains with low glass transition temperature, is responsible for the healing phenomenon. Furthermore, the healing efficiency is found to be enhanced when the separated pieces are recombined immediately after cutting. This result indicates that the cut surface has marked molecular mobility owing to the destruction of crystallites during the cutting process, which is supported by differential scanning calorimetry (DSC) measurements. The marked molecular mobility at the surface is, however, observed only for a short period after cutting, because further crystallization after cutting restricts the molecular motion.

In this study, flexible transparent hybrid films with low thermal expansion coefficient were prepared by combination of alumina fillers and polymerizable/non-polymerizable surface modifiers with carboxyl group. Four types of alumina fillers with different shape and size were used in this study, and could modify with surface modifiers containing carboxyl groups by electrostatic interaction and disperse homogeneously in resulting hybrid films regardless of the shape and size. So the hybrid films obtained showed high transmittance around 90%T, and it was considered, from transmission electron microscopic analysis, alumina fillers were dispersed at near original filler size, without aggregation. Moreover, thermal mechanical analysis cleared that the use of pillar or fiber type filler is more effective to reduce CTE compared with plate type fillers, especially CTE of hybrid film prepared with fiber type filler was drastically decreased to 17 ppm/K, while the influence by the difference of filler shape/size was not observed on tensile properties, surface hardness. By use of fiber type alumina filler and combination of polymerizable surface modifier and non-polymerizable surface modifier which seems to interact with matrix, for optimizing of the crosslink density, it was possible to reduce CTE, while the good mechanical properties was kept. Finally, hybrid film indicating low CTE value as 19 ppm/K, high flexibility (windable against 0.4 mm radius steel bar), and good tensile properties and surface hardness which were equal to or higher than those of matrix could prepared.

The effect of a substitution site on orientation birefringence for cellulose triacetate (CTA) was investigated by the addition of xylan ester. Since CTA has three substitution sites (C-2, C-3, and C-6) while xylan ester has two substitution sites (C-2 and C-3), the change of birefringence by xylan acetate (XylAc) is attributed to the contribution of the C-6 acetyl group. Dynamic mechanical analysis and thermal measurements showed a single glass transition peak, indicating that XylAc is miscible with CTA at any compositions. The orientation birefringence (Δn) of CTA/XylAc films stretched beyond the glass transition temperature increased with increasing the XylAc content. The result for the stretched film suggested that the contribution of acetyl group in the C-2 and C-3 sites to Δn is positive while that in the C-6 is negative. The negative sign for the C-6 site is in agreement with the result simulated by using the molecular dynamics method. In addition, Δn of CTA films containing xylan propionate (or butyrate) indicated that the propionyl and butyryl groups in the C-2 and C-3 sites show positive birefringence similar to the acetyl group.

The localization of multi-walled carbon nanotubes (MWCNTs) in immiscible polymer blends composed of polycarbonate (PC) and poly(ethylene terephthalate) (PET) is studied. Although partial miscibility is confirmed for the blend, presumably owing to the transesterification reaction, the MWCNT addition is found to have no influence on the miscibility. Moreover, morphological investigation and solvent extraction experiments reveal that MWCNTs are preferentially localized in PET phase. Thermal behavior demonstrates that MWCNTs act as an effective nucleating agent for PET, leading to the increment in crystallization temperature and crystallinity of PET. Tensile properties of PC/PET blends, i.e., Young's modulus, yield strength, and ultimate strength, are significantly improved by the addition of MWCNTs. POLYM. COMPOS., 38:1103–1111, 2017. © 2015 Society of Plastics Engineers

A new method to localize poly(methyl methacrylate) (PMMA) at the surface of a miscible blend with polycarbonate (PC) is demonstrated. Low-molecular-weight PMMA, which is found to be miscible with PC, is used in this study. After annealing the PC/PMMA blend in a temperature gradient, PMMA is found to localize on the high-temperature side, as detected by infrared spectroscopy and molecular weight measurements. Furthermore, the sample exhibits good transparency even after annealing. This phenomenon is notable because it is applicable to enhancing the anti-scratch properties of PC.

A contradict interphase transfer of multi-walled carbon nanotubes (MWCNT) is detected in the immiscible polymer pair of polyethylene (PE) and polycarbonate (PC). When laminated sheets composed of PE with MWCNTs and PC are annealed in the molten state of both polymers, MWCNTs are found to move from PE to PC. This transfer phenomenon is originated from the difference in the interfacial tension with the aid of Brownian motion. On the contrary, MWCNTs prefer to reside in the PE phase in the blend of PE, PC and MWCNTs, even when MWCNTs are first dispersed in PC. This result indicates that MWCNTs transfer from PC to PE. The opposite direction of the transfer is attributed to the PE molecules being adsorbed on the surface of MWCNTs, which are generated during mixing.

Phase separation in plasticized cellulose triacetate (CTA) films is investigated to produce a microporous film that can be used in optical devices. Hot-stretched CTA films containing diisodecyl adipate (DIDA) show negative orientation birefringence similar to the hot-stretched pure CTA. After extracting DIDA from the stretched films by immersion into an organic solvent, however, the films exhibit positive birefringence. Moreover, the magnitude of the birefringence increases with the wavelength, known as extraordinary dispersion, which is an essential property in the preparation of an ideal quarter-wave plate. Numerous ellipsoidal pores with micro-scale were detected in the film after the immersion, indicating that DIDA were segregated and formed ellipsoidal domains in the CTA matrix during annealing and stretching. These results indicate that extraordinary wavelength dispersion is given by the combinations of orientation birefringence from CTA and form birefringence from micropores. Furthermore, it was found that annealing time and stretching condition affect the phase separation as well as the shape and size of pores.

Glass transition temperature ( T g ) and vibrational properties at the chain end of polystyrene (PS) were selectively determined by a novel method utilizing Fourier transform infrared (FT-IR) spectroscopy. In this method, PSs having almost the same number average molecular weight ( M n ) but selectively deuterated at different sites, midchain (M-PS, M n = 10.7 kDa) or chain end (E-PS, M n = 10.3 kDa), were synthesized and the asymmetric stretching vibration of the main chain CD 2 ( ν as (CD 2 )) were analyzed in detail. We found that the temperature dependence of the ν as (CD 2 ) frequency shows a clear inflection at the calorimetric T g of PS. The inflection temperature was defined as T g,FTIR , which represents the T g at the local region around the deuterated sites. Although higher segmental mobility at the chain end had been shown above the T g in our earlier work, this study found that the T g,FTIR s of the M-PS and E-PS are the same. From this result, it was concluded that the chain ends move cooperatively with numerous neighboring other segments, averaging out those mobilities at temperatures around the T g . On the other hand, the ν as (CD 2 ) frequency of the E-PS was by a few cm −1 higher than that of the M-PS for any temperature. This was explained in terms of the discontinuity of the repeat unit at the chain end resulting in reduced interactions between repeat units along the chain.

The effect of flexible chain on orientation dynamics of a small additive molecule in cellulose acetate propionate (CAP) films is investigated during stretching by means of measurements of birefringence and polarized Fourier-transform infrared (FT-IR) spectrum. The orientation birefringence is enhanced by the additives such as ethylene 2,6-naphthalate (C_2Np) and hexamethylene 2,6-naphthalate (C_6Np) oligomers, suggesting that the additives orient parallel to the CAP chain due to an intermolecular orientation correlation called as the nematic interaction (NI). At a high drawing temperature, the orientation of C_2Np is stronger than that of C_6Np, indicating that the flexible alkyl chain reduces the intermolecular NI with CAP. In contrast, C_6Np orients to the stretching direction rather than C_2Np at a low temperature. The polarized FT-IR spectra show that the orientation of rigid part in C_6Np is delayed from that of the flexible group and matrix CAP chain. Consequently, the contribution of C_6Np to birefringence and its wavelength dependence become stronger with increasing the draw ratio.

A method to control the 3D refractive indices and wavelength dispersion of birefringence of polymer films by uniaxial stretching with addition of various low-molecular-weight compounds (LMCs) with strong polarizability anisotropy is developed. Biomass-derived cellulose triacetate (CTA) films containing a small amount of crystallites at the stretching temperature are found to show planar deformation to some degree only by uniaxial stretching. Although molecular orientation evaluated from the in-plane and out-of-plane birefringences of pure CTA seems consistent with uniaxial deformation, LMC addition pronounces the deviation of the refractive index from uniaxial symmetry. Rod-shaped molecules are found to greatly enhance both in-plane and out-of-plane birefringences because of their marked orientation in the stretching direction. Conversely, the out-of-plane birefringence increases more than the in-plane one upon addition of disk-shaped molecules, because the LMC molecules tend to be embedded in the film plane. Consequently, 3D refractive indices of CTA can be controlled only by uniaxial stretching, not biaxial one, with an aid of an anisotropic LMC.

The melting point of a conventional isotactic polypropylene (PP) was enhanced by a rapid annealing procedure of an extruded sheet composed of β trigonal form crystals having thick lamellae, which was prepared by T-die processing with a specific β-nucleating agent, N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide. Although the melting point of PP with α monoclinic form, prepared by a conventional processing method, is known to be located around at 165°C, the sample obtained by the present technique showed a higher melting point, 170°C. The phase transformation from β-to α-form crystals, retaining the lamellar thickness, was responsible for the melting point elevation.

We examined birefringence in a stretched film of cellulose triacetate (CTA) after extraction of an immiscible component. The CTA film plasticized by di(2-ethylhexyl) adipate (DOA), which was added as the immiscible additive, exhibited negative birefringence to the same degree as the pure CTA film. Following removal of DOA from the film by immersion into methanol, the birefringence of the blend film changed dramatically from negative to positive. Moreover, the wavelength dependence also changed from ordinary to extraordinary, in which the absolute value of birefringence increases with wavelength. Scanning electron microscope (SEM) images revealed nanoscale ellipsoidal pores in the film after the extraction, suggesting that DOA was segregated and formed ellipsoidal domains in the CTA matrix during annealing and stretching. According to an optical theory for the nanoporous structure, we found that the form birefringence contributes to control of the optical properties of the CTA film. This phenomenon could be utilized in the design of high-performance optical films, such as quarter waveplate, because sign and wavelength dispersion of birefringence can be controlled even for a single component film.

We examined the effects of thermal modification under flow field on the rheological properties of linear low-density polyethylene (LLDPE) with high molecular weight, low-density polyethylene (LDPE), and their blends, without thermal stabilizer. Although structural changes during processing are not detected by size extrusion chromatography or nuclear magnetic resonance spectroscopy (NMR), linear viscoelastic properties changed greatly, especially for the LLDPE. A cross-linking reaction took place, leading to, presumably, star-shaped long-chain branches. Consequently, the modified LLDPE, having high zero-shear viscosity, became a thermo-rheologically complex melt. Moreover, it should be noted that the drawdown force, defined as the uniaxial elongational force at a constant draw ratio, was significantly enhanced for the blends. Enhancement of elongational viscosity was also detected. The drawdown force and elongational viscosity are marked for the thermally-modified blend as compared with those for the blend of thermally-modified pure components. Intermolecular cross-linking reactions between LDPE and LLDPE, yielding polymers with more than two branch points per chain, result in marked strain-hardening in the elongational viscosity behavior even at small strain. The recovery curve of the oscillatory modulus after the shear modification is further evidence of a branched structure.

Effect of the addition of poly(ethylene glycol) terminated by benzoate (PEG-BA) on the crystallization behavior and dynamic mechanical properties of poly(L-lactic acid) PLLA is studied as compared with poly(ethylene glycol) (PEG-OH). It is found that PEG-BA shows good plasticizing effect and the Flory-Huggins interaction parameter with PLLA is negative. Because PEG-OH having the same degree of polymerization is immiscible with PLLA, the end group in PEG-BA, i.e., benzoate, plays an important role in the miscibility. Furthermore, PEG-BA does not induce the PLLA degradation at melt-processing, whereas PEG-OH leads to the hydrolysis degradation. Finally, the addition of PEG-BA pronounces the crystallization rate of PLLA at low crystallization temperatures and thus enhances the degree of crystallinity. Consequently, the temperature dependence of dynamic mechanical properties are similar to those of isotactic polypropylene.

Thermal expansion behavior and viscoelastic properties of antiplasticized polycarbonate (PC) are studied employing p-terphenyl (p-tPh) as an antiplasticizer. The rheological characterization reveals that the free volume fraction at the glass transition temperature and thermal expansion coefficient of the free volume in the rubbery region are unchanged by the p-tPh addition. However, the linear coefficient of thermal expansion in the glassy region is found to be reduced, which can be attributed to the reduction of free volume in the glassy state. Since the antiplasticized PC exhibits high modulus with a low thermal expansion coefficient, its suitability as a replacement for inorganic glasses will be considered.

Injection-molded isotactic polypropylene (PP) containing a small amount of the β-nucleating agent N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide exhibits a unique molecular orientation that is similar to that of plywood. X-ray diffraction and birefringence distribution measurements revealed that PP chains in β-form crystals are oriented perpendicular to the flow direction through epitaxial crystallization on the needle-shaped nucleating agent, even in the skin layer. Furthermore, PP chains in α-form crystals orient along the flow direction through flow-induced crystallization. Although the skin has a ‘woven-cloth’ structure in which the two crystalline forms are oriented perpendicular to each other, it shows positive birefringence, on average, because of the stronger orientation of α-form crystals. In the core, not only β-form crystals but also α-form crystals are oriented perpendicular to the flow direction. As the average orientation direction in the skin layer is perpendicular to that in the core, the dynamic tensile modulus in the flow direction is almost identical to that in the transversal direction, resulting in a low level of mechanical anisotropy. Moreover, the anisotropy in thermal expansion is greatly reduced by the extraordinary molecular orientation. The injection-molded isotactic polypropylene (PP) containing a specific nucleating agent exhibits unique molecular orientation. Although the skin layer has ‘woven-cloth’ structure, in which α- and β-form crystals orient perpendicular to each other, it shows positive birefringence on average because of the stronger orientation of α-form crystals. In the core, both crystals show perpendicular orientation to the flow direction. As the average orientation direction in the skin layer is perpendicular to that in the core, the anisotropy in mechanical properties and thermal expansion is greatly reduced.

Orientation birefringence and its wavelength dispersion in blends of cellulose acetate propionate (CAP) and aromatic additive molecules having various alkyl chains were investigated, in order to evaluate the effect of the chemical structure on the optical properties. We found that the additive improved the orientation birefringence of CAP, meaning that the additive orientation is parallel to CAP chains via the “nematic interaction (NI)” reflecting the intermolecular orientation correlation. The NI strength was evaluated by using a theory concerning the molecular orientation. The result demonstrates that the alkyl chain length in the additive molecule strongly affects the orientation correlation. Although the intrinsic birefringence monotonically decreases with the alkyl chain length, the NI strength shows the highest value between the additive with propionyl group and CAP. From the result, the contribution of birefringence from the aromatic molecule, which is determined by the intrinsic birefringence and orientation function, needs to be considered to design the optical films with high performances. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3465–3472, 2013