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Nucleic acids are a special class of negatively charged polymers, and they can complex with cationic small molecules and polymers to form polyelectrolyte complexes of rich morphology. The initial a...

Low pressure materials pre-treatment process has been developed as an alternative to the existing high-temperature sludge drying, limestone calcination, and limonite dehydroxylation. Using the thermodynamic equilibrium relationship between temperature and pressure represented by the Clausius-Clapeyron equation, the operational temperature of these reactions could be lowered at reduced pressure for increased energy efficiency. For industrial sludge drying, the evaporation rate was controlled by interfacial kinetics showing a constant rate with time and significant acceleration in the reaction could be observed with reduced pressure. At this modified reaction rate under low pressure, the rate was also partially controlled by mass transfer. Temperature of limestone calcination was lowered, but the reaction was limited at the calculated equilibrium temperature of the Clausius-Clapeyron equation and slightly higher temperatures were required. The energy consumption during limestone calcination and limonite dehydroxylation were evaluated, where lower processing pressures could enhance the energy efficiency for limestone calcination, but limonite dehydroxylation could not achieve energy-savings due to the greater power consumption of the vacuum pump under lower pressure and reduced temperatures.

Direct fabrication of titanium (Ti) and niobium (Nb) alloys by direct magnesiothermic reduction from the respective initial metal oxides and complex oxides has been studied. TiO2, Nb2O5, and complex TiNb2O7 oxides were used as raw materials with Mg used as a reductant. To ensure a high chemical potential of the reactants to drive the spontaneous magnesiothermic reduction of the oxide mixtures, excess Mg five times higher than the required stoichiometric molar ratio was added. Samples were heated in a glove box under recycled and purified Ar atmosphere at 1073 K (800 °C) for 10 h. After the reduction of TiO2, intermediate oxide phases of Ti6O could still be observed, but reduction of Nb2O5 and TiNb2O7 showed metallic Nb and Ti-Nb to be present with negligible oxides according to the scanning electron microscope-energy dispersive spectroscopy and x ray diffraction analysis. This indicated that direct fabrication of Ti-Nb alloys through a complex TiNb2O7 oxide is possible and can be more efficient than alloying pure metallic elements of Ti and Nb.

We report low dark current small molecule organic photodetectors (OPDs) with an inverted geometry for image sensor applications. Adopting a very thin MoOx:Al cathode interlayer (CIL) in the inverted OPD with a reflective top electrode results in a remarkably low dark current density (Jd) of 5.6 nA/cm2 at reverse bias of 3 V, while maintaining high external quantum efficiency (EQE) of 56.1% at visible wavelengths. The effectiveness of the CIL on the diode performance has been further identified by application to inverted OPDs with a semi-transparent top electrode, leading to a significantly low Jd of 0.25 nA/cm2, moderately high EQE540 nm of 25.8%, and subsequently high detectivity of 8.95 × 1012 Jones at reverse bias of 3 V. Possible origins of reduced dark currents in the OPD by using the MoOx:Al CIL are further described in terms of the change of interfacial energy barrier and surface morphology.

Reciprocating friction characteristics of magneto-rheological (MR) fluid for aluminum under a magnetic field at different loads and oscillation frequencies were studied when MR fluids were worked in reciprocating motions such as in dampers for automobiles, and surface polishing and other finishing. Thus, experiments were carried out to evaluate the reciprocating friction characteristic of MR fluid for aluminum. The obtained data from the tests are sorted in groups depending on various loads and oscillation frequencies, to analyze the relationship between test condition and travel cycle. Surfaces of specimens were compared by measuring the surface roughness and observing the surface images. The performance of reciprocating friction characteristics of MR fluid for aluminum is evaluated through analyzing the experiment results.

The foams of a poly(lactic acid) modified by the reactive compounding were produced with the batch foaming technique using supercritical . Experiments were performed at and 12~24 MPa. The blowing ratio and foam structure were significantly affected by changing the temperature and pressure conditions in the foaming process. The blowing ratio first increased with increasing foaming temperature and saturation pressure, reached a maximum and then decreased with a further increase in the foaming temperature and saturation pressure. Decreasing the rate of depressurization permitted a longer period of cell growth and therefore larger microcellular structures were obtained.

Room temperature baroplastic processing of polystyrene (PS) and poly(n-butyl acrylate) (PBA) was investigated through the formation of nanoblends of their polymer nanoparticles. Instead of core-shell or block copolymer structures, PS and PBA nanoparticles were synthesized separately through aqueous emulsion polymerization and then mixed and precipitated. The resulting nano-blends provided semi-transparent molding at 25 °C under applied pressure, resembling that of core-shell and block copolymer baroplastic systems. Differential scanning calorimetry measurements of the compressed samples revealed the presence of intermixing glass transition between the two components, which indicated baroplastic processing. However, PS/poly(lauryl methacrylate) blends exhibited no intermixing glass transition, indicating no pressure-induced miscibility between the two phases.

The silane coupling agent, 3-(trimethoxysilyl)propyl methacrylate (-MPTS), was grafted on the surface of alumina nanoparticles. We used the surface modified nanoparticles in the hard coating layer for in-mold decoration (IMD) foils and evaluated the coating properties such as hardness and anti-abrasion property. The effects of electron beam (EB) irradiation on color layer and anchor layer of IMD foils were observed through the difference in color and the cross-cut tape test, respectively. Also, cure kinetics as studied quantitatively under various reaction temperatures by analysis of surface properties and Fourier transform infrared (FTIR) spectroscopy. From these results, we constructed database for the commercial exploitation of EB curing system.

The foaming of poly(butylene succinate) (PBS) using supercritical CO2(scCO2) was studied. In order to improve the melt strength, PBS was modified using the reactive compounding technique. Rapid decompression of scCO2-saturated PBS at a temperature above the depressed Tm yielded expanded microcellular foams. The resulting foam structure could be controlled by manipulating process conditions. Experiments varying the foaming temperature while holding other variables constant showed that higher temperatures produced larger cells and reduced cell densities. Higher saturated pressures led to higher nucleation densities and smaller cell sizes. Decreasing the rate of depressurization permitted a longer period of cell growth and therefore larger cells were obtained.

Homopolymer distribution in block copolymer/homopolymer blends was investigated as a function of homopolymer concentration and homopolymer molecular weight. The deuterated poly(methyl methacrylate) or polystyrene was blended with a deuterated polystyrene-poly(methyl methacrylate) diblock copolymer up to a concentration of 20 wt%. Samples were characterized by small-angle X-ray scattering (SAXS), neutron reflectivity and transmission electron microscopy. The block copolymer with a thin-film geometry formed alternating lamellar microdomains oriented parallel to the substrate surface. By adding the homopolymer, the microdomain structure was significantly disturbed. As a consequence, a poorly ordered morphology appeared when the homopolymer concentration exceeded 15 wt%. Increasing the homopolymer concentration and/or the homopolymer molecular weight caused the microdomains to swell less uniformly, resulting in segregation of the homopolymer toward the middle of the microdomains.

Synthetic aliphatic biodegradable poly(butylene succinate) (PBS) nanocomposites with multiwalled carbon nanotube (MWNT) were investigated to study the effects of the preparation method and MWNTs on physical characteristics of biodegradable polymer nanocomposite foams. PBS nanocomposites were prepared by the solution blending and melt mixing methods. Nanocomposites of PBS/MWNT were also prepared by the SOAM method, where the solution-blended nanocomposites were further mixed in the melt state. The dispersion of MWNTs in the PBS matrix was characterized by FT-Raman spectroscopy, field-emission scanning electron microscopy (FE-SEM), and field-emission transmission electron microscopy (FE-TEM). The mechanical and thermal properties of the PBS nanocomposites were measured using a universal test machine (UTM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Nanocomposite foams with high-density closed cells were prepared by using a chemical blowing agent (CBA) that acted as a cell...

The electron beam (EB) induced curing of a typical resin designed for the hard coating layer of in-mold decoration foils was investigated. The samples were irradiated with different doses of EB and the curing reaction was monitored by Fourier transform infrared (FTIR) spectroscopy. The change in coating properties such as surface hardness and anti-abrasion property was studied as a function of increasing dose. The effect of the addition of nano-particles on the improvement of coating properties was also examined. It was expected that the experimental results could be used for the commercial exploitation of the EB curing system comparable to the ultraviolet (UV) curing system.

Poly(butylene succinate) (PBS)/organoclay nanocomposites were prepared by both solution blending and melt mixing methods. In addition, nanocomposites of PBS/organoclay were also prepared by a two-step process where the solution blended mixture is subsequently compounded in the melt state using a torque rheometer (SOAM method). We then investigated thermal and mechanical properties of the PBS/organoclay nanocomposite at first and determined an optimum organoclay content for the preparation of nanocomposite foams. All PBS/organoclay nanocomposite foams are found to possess closed sphericalshaped cells without any rupture when examined by an optical microscopy. The blowing ratio also increased with the increase in the blowing temperature and time, with the maximum blowing ratio of 19. Furthermore, the addition of a small amount of organoclay is found to allow the cell size to follow Gaussian distribution. POLYM. ENG. SCI., 51:1316–1324, 2011. a 2011 Society of Plastics Engineers

Nanocomposites of biodegradable poly(butylene succinate) (PBS) and carbon nanofibers (CNFs) were prepared by three different methods, that is, solution blending, melt compounding, and solution and subsequent melt blending (SOAM) method, among which the SOAM method, where nano-scale fillers and polymer matrix are solution-blended and subsequently melt-mixed in a torque rheometer, is a two-step process for obtaining polymer nanocomposite. Dispersion of CNFs in the PBS matrix was characterized by FE-SEM, while thermal and mechanical properties were analyzed by thermogravimetric ananlysis (TGA) and universal test machine (UTM), respectively. The PBS/CNF nanocomposites were then converted to foams by employing a chemical blowing agent (CBA) in the melt. The presence of CNFs increased the melt viscosity of PBS so that the PBS/CNF nanocomposite foams were produced without modifying the chemical structure of the PBS. Nanocomposite foams prepared by the SOAM method showed higher physical properties compared with t...

The spherulite morphology and crystallization behavior of poly(ethylene terephthalate) (PET)/poly(trimethylene terephthalate) (PTT) blends were investigated with optical microscopy (OM), small-angle light scattering (SALS), and small-angle X-ray scattering (SAXS). The thermal analysis showed that PET and PTT were miscible in the melt over the entire composition range. The rejected distance of non-crystallizable species, which was represented in terms of the parameter δ, played an important role in determining the morphological patterns of the blends at a specific crystallization temperature regime. The parameter δ could be controlled by variation of the composition, the crystallization temperature, and the level of transesterification. In the case of two-step crystallization, the crystallization of PTT commenced in the interspherulitic region between the grown PET crystals and proceeded until the interspherulitic space was filled with PTT crystals. The spherulitic surface of the PET crystals acted as nucleation sites where PTT preferentially crystallized, leading to the formation of non-spherulitic crystalline texture. The SALS results suggested that the growth pattern of the PET crystals was significantly changed by the presence of the PTT molecules. The lamellar morphology parameters were evaluated by a one-dimensional correlation function analysis. The blends that crystallized above the melting point of PTT showed a larger amorphous layer thickness than the pure PET, indicating that the non-crystallizable PTT component might be incorporated into the interlamellar region of the PET crystals. With an increased level of transesterification, the exclusion of non-crystallizable species from the lamellar stacks was favorable due to the lower crystal growth rates. As a result, the amorphous layer thickness of the PET crystals decreased as the annealing time in the melt state was increased.

The microdomain structures and crystallization behavior of the binary blends of poly(methyl methacrylate)-b-poly(pentafluorostyrene)-b-poly(methyl methacrylate) (PMMA-PPFS-PMMA) triblock copolymer with a low molecular weight poly(vinylidene fluoride) (PVDF) were investigated by small-angle X-ray scattering (SAXS), small-angle light scattering (SALS), transmission electron microscopy (TEM), optical microscopy, and differential scanning calorimetry (DSC). A symmetric, PMMA-PPFS-PMMA triblock copolymer with a PPFS weight fraction of 33% was blended with PVDF inN,N-dimethylacetamide (DMAc). In the wide range of PVDF concentration between 10.0 and 30.0 wt%, PVDF was completely incorporated within the PMMA microdomains of PMMAPPFS-PMMA without further phase separation on a micrometer scale. The addition of PVDF altered the phase morphology of PMMA-PPFS-PMMA from well-defined lamellar to disordered. The crystallization of PVDF significantly disturbed the domain structure of PMMA-PPFS-PMMA in the blends, resulting in a poorly-ordered morphology. PVDF displayed unique crystallization behavior as a result of the space constraints imposed by the domain structure of PMMA-PPFS-PMMA. The pre-existing microdomain structures restricted the lamellar orientation and favored a random arrangement of lamellar crystallites.

In order to obtain crosslinked poly(butylene succinate) (PBS) foams with a closed-cell structure, a commercial-grade PBS was first modified in the melt using two different branching agents to increase the melt viscosity. The rheological properties of the branched and crosslinked PBS were examined by varying the amount of the branching agents. The complex viscosity of the crosslinked PBS increased with increasing amount of the branching agent. However, it decreased with increasing frequency. When 2 phr of the branching agent was added to PBS, the storage modulus (G′) was higher than the loss modulus (G″) throughout the entire frequency range, showing that the addition of a branching agent increases the melt viscosity and elasticity of PBS effectively. Closed-cell PBS foams were prepared by mixing the chemical blowing agent with the crosslinked PBS. The effect of the foaming conditions such as temperature and time, and the amount of the crosssslinking agent on the structure of the expanded PBS foams were also investigated.

Metal filament based organic memory device has unique advantages of long retention time and thermal stability. However, it has suffered from a large variation in the switching delay time (∼ 100 ms), in spite of the fast real switching time of hundreds nanoseconds. Among many possible reasons for the broad delay time, the effect of structural nonuniformity in active area was mainly considered in this work. To solve this problem, we introduced an embossed structure into previous organic memory device, which significantly narrowed the distribution of the delay time. With this device, we could directly observe that the switching preferentially occurs at the summits of the embossed structure through optical microscope image.

The spherulite morphology and crystallization behavior of poly(trimethylene terephthalate) (PTT)/poly(ether imide) (PEI) blends were investigated with optical microscopy (OM), small-angle light scattering (SALS), and small-angle X-ray scattering (SAXS). Thermal analysis showed that PTT and PEI were miscible in the melt over the entire composition range. The addition of PEI depressed the overall crystallization rate of PTT and affected the texture of spherulites but did not alter the mechanism of crystal growth. When a 50/50 blend was melt-crystallized at 180 °C, the highly birefringent spherulite appeared at the early stage of crystallization (t < 20 min). After longer times, the spherulite of a second form was developed, which exhibited lower birefringence. The SALS results suggested that the observed birefringence change along the radial direction of the spherulite was mainly due to an increase in the orientation fluctuation of the growing crystals as the radius of spherulite increased. The lamellar morphological parameters were evaluated by a one-dimensional correlation function analysis. The amorphous layer thickness showed little dependence on the PEI concentration, indicating that the noncrystallizable PEI component resided primarily in the interfibrillar regions of the growing spherulites.

The morphological development and crystallization behavior of a poly(ethylene terephthalate)/poly(hydroxyl ether of bisphenol A) (phenoxy) blend were studied with time-resolved light scattering, optical microscopy, differential scanning calorimetry, and small-angle X-ray scattering (SAXS). During annealing at 280 °C, liquid–liquid phase separation via spinodal decomposition proceeded in the melt-extruded specimen. After the formation of a domain structure, the blend slowly underwent phase homogenization by the interchange reactions between the two polymers. Specimens annealed for various times (ts) at 280 °C were subjected to a temperature drop and the effects of liquid-phase changes on crystallization were then investigated. The shifts in the position of the cold-crystallization peaks indicated that the crystallization rate is associated with the composition change of the separated phases as well as the change of the sequence distribution in polymer chains during annealing. The morphological parameters at the lamellar level were determined by a correlation function analysis on the SAXS data. The crystal thickness (lc) increased with ts, whereas the amorphous layer thickness (la) showed little dependence on ts. Observation of a constant la value revealed that a large number of noncrystallizable species formed by the interchange reactions between the two polymers were excluded from the lamellar stacks and resided in the interfibrillar regions, interspherulitic regions, or both. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 223–232, 2008

This report presents a new technical approach for evaluating the fiber orientation of composites using small-angle light scattering (SALS). Glass fiber (GF)/polypropylene (PP) composites with different fiber orientations were prepared by drawing compression-molded specimens. The drawn samples were remelted and then annealed at 150 °C in order to induce a crystalline structure on the fiber surface, and then underwent SALS analysis. The samples showed a combination of circular and streak patterns. The model calculations demonstrated that the number of nuclei on the fiber surface and the thickness of the transcrystalline layer affected the sharpness and intensity of the streak pattern. In addition, the azimuthal angle of the streak pattern was found to be dependent on the direction of the transcrystalline layer, which correlated with the fiber direction. This correlation suggests that the fiber orientation in the composites can be easily evaluated using SALS.

This study examined the microdomain structures and the crystallization behavior in binary blends consisting of an asymmetric block copolymer and a homopolymer using small-angle X-ray scattering, optical microscopy and differential scanning calorimetry. A polystyrene-block-poly(methyl methacrylate) copolymer (PS-b-PMMA) was mixed with a low molecular weight poly(vinylidene fluoride) (PVDF), where the PS-b-PMMA had a 0.30 wt fraction of the PMMA block. At a PVDF concentration of

We employed thin film blends of diblock copolymers with functional homopolymers as a simple strategy to incorporate organic functional materials into nanodomains of diblock copolymers without serious synthesis. A blend pair of polystyrene–poly(methyl methacrylate) (PS–PMMA) diblock copolymers and poly(vinylidene fluoride) (PVDF) was selected as a model demonstration because PVDF is a well-known ferroelectric polymer and completely miscible with amorphous PMMA. Thin films of symmetric PS–PMMA copolymers provided the nanometer-sized PMMA lamellae, macroscopically parallel to the substrate, in which PVDF chains were dissolved. Thus, amorphous PVDF chains were effectively confined in the PMMA lamellae of thin film blends. The location of PVDF chains in the PMMA lamellae was investigated by the dependence of the lamellar period on the volume fraction of PVDF, from which we found that PVDF chains were localized in the middle of the PMMA lamellae. After the crystallization of PVDF, however, some of PVDF migrated to the surface of the film and formed small crystallites.

Poly(l-lactic acid-co-succinic acid-co-1,4-butane diol) (PLASB) was synthesized by direct condensation copolymerization ofl-lactic acid (LA), succinic acid (SA), and 1,4-butanediol (BD) in the bulk using titanium(IV) butoxide as a catalyst. The weight-average molecular weight of PLASB was 2.1 × 105 when the contents of SA and BD were each 0.5 mol/100 mol of LA. Electrospinning was used to fabricate porous membranes from this newly synthesized bioabsorbable PLASB dissolved in mixed solvents of methylene chloride and dimethylformamide. Scanning electron microscopy (SEM) images indicated that the fiber diameters and nanostructured morphologies of the electrospun membranes depended on the processing parameters, such as the solvent ratio and the polymer concentration. By adjusting both the solvent mixture ratio and the polymer concentration, we could fabricate uniform nanofiber non-woven membranes. Cell proliferation on the electrospun porous PLASB membranes was evaluated using mouse fibroblast cells; we compare these results with those of the cell responses on bulk PLASB films.

The morphology development and crystallization behavior of an extruded poly(ethylene terephthalate)/polycarbonate blend were studied with optical microscopy, light scattering, and differential scanning calorimetry (DSC). During annealing at 280°C, liquid-liquid phase separation via spinodal decomposition proceeded in a melt-extruded specimen. After the formation of the domain structure, the blend slowly underwent phase homogenization by transesterification between the two polymers. The specimen, annealed for various times (t s 's) at 280°C, was subjected to a temperature drop to 180°C for the isothermal crystallization, and then the effects of liquid-phase changes on crystallization were investigated. The crystal growth rate decreased with t s . The slow crystallization with a large t s value was associated with the composition change of the separated phases and the change of the sequence distribution in the polymer chains during annealing. The influence of t s on the endothermic behavior of the samples was examined. As t s increased, the recrystallization rate was retarded during the DSC scan, displaying multiendothermic behavior. The DSC data also suggested that the increased level of transesterification would give rise to a higher number of species being rejected from the primary crystals, leading to enhanced secondary crystallization.

We have studied the lamellar-level morphology of poly(ethylene terephthalate) (PET)/polycarbonate (PC) blends using small-angle X-ray scattering (SAXS). Measurements were made as a function of the holding time in the melt. We determined the morphological parameters at the lamellar level by correlation function analysis of the SAXS data. An increased amorphous layer thickness was identified in the blend, indicating that some PC was incorporated into the interlamellar regions of PET during crystallization. The blend also exhibits a larger lamellar crystalline thickness (l c ) than that of pure PET. A possible reason for the increase inl c is that the inclusion of the PC molecules in the interlamellar regions causes an increase in the surface free energy of folding. At the early stage of isothermal crystallization, we observed a rapid drop in the value ofl c in the blend; this finding indicates that a relatively large fraction of secondary crystals form during the primary crystallization. In contrast, the value ofl c for the sample that underwent a prolonged holding time increased with time in the secondary crystallization-dominant regime; this observation suggests that the disruption of chain periodicity, which results from transesterification between the two polymers, favors the development of fringed micellar crystals that have larger values ofl c , rather than the development of normal chain-folded crystals.

The liquid–liquid (L–L) phase separation and crystallization behavior of poly(ethylene terephthalate) (PET)/poly(ether imide) (PEI) blend were investigated with optical microscopy, light scattering, and small angle X-ray scattering (SAXS). The thermal analysis showed that the concentration fluctuation between separated phases was controllable by changing the time spent for demixing before crystallization. The L–L phase-separated specimens at 130 °C for various time periods were subjected to a temperature-jump of 180 °C for the isothermal crystallization and then effects of L–L phase separation on crystallization were investigated. The crystal growth rate decreased with increasing L–L phase-separated time (ts). The slow crystallization for a long ts implied that the growth path of crystals was highly distorted by the rearrangement of the spinodal domains associated with coarsening. The characteristic morphological parameters at the lamellar level were determined by the correlation function analysis on the SAXS data. The blend had a larger amorphous layer thickness than the pure PET, indicating that PEI molecules in the PET-rich phase were incorporated into the interlamellar regions during crystallization.

Morphology in an extruded poly(ethylene terephthalate)/poly(ethylene-2,6-naphthalate) was investigated using time-resolved light scattering, optical microscope and small-angle X-ray scattering. During annealing at 280 °C, the domain structure via spinodal decomposition preceded, the transesterification followed, and then the transesterification between the two polyesters induced the dissolution of the liquid–liquid (L–L) phase separation, i.e. the homogenization. The annealed specimen for various time periods (ts) at 280 °C was subjected to a temperature-drop to 120 °C for the isothermal crystallization and then the effects of liquid phase morphology on crystallization was investigated. With ts, the Hν (cross-polarization) light scattering patterns exhibited the dramatic change from a four-leaf clover pattern with maximum intensity at azimuthal angle 45° (×-type scattering pattern) to a diffuse pattern of circular symmetry and then a four-leaf clover pattern with maximum intensity at azimuthal angles 0 and 90° (+-type scattering pattern). This suggests that the crystalline structure depends on the level of the block and/or random copolymer produced by the transesterification during annealing. The Hν scattering patterns reflected differences in the principle polarizability of the crystalline lamellae with respect to the spherulitic radius. On the other hand, the long period LB, an average distance between two adjacent crystalline lamellae, increased with ts at 280 °C. The dependence of LB on ts was explained by the change in the crystallization rate G.

The supermolecular structures of poly(ethylene terephthalate) (PET), poly(ethylene 2,6-naphthalate) (PEN), and their blend were investigated with optical microscopy and small angle light scattering. With increasing the crystallization temperature, incomplete spherulitic texture was developed for the PET samples. At a high crystallization temperature of 220°C, the light scattering pattern represented a random collection of uncorrelated lamellae. The general morphological appearances for the PEN samples were similar to that of the PET. A notable feature was that the spherulites of the PEN formed at 200°C showed regular concentric bands arising from a regular twist in the radiating lamellae. The spherulitic morphology of the PET/PEN blend was largely influenced by the changes of the sequence distribution in polymer chains determined by the level of transesterification. The increased sequential irregularity in the polymer chains via transesterification caused a morphological transition from a regular folded crystallite to a tilted lamellar crystallite.

The lamellar-level morphology of an extruded poly(ethylene terephthalate) (PET)/poly(ethylene-2,6-naphthalate) (PEN) blend was investigated with small-angle X-ray scattering (SAXS). Measurements were made as a function of the annealing time in the melt and the crystallization temperature. The characteristic morphological parameters at the lamellar level were determined by correlation function analysis of the SAXS data. At a low crystallization temperature of 120 °C, the increased amorphous layer thickness was identified in the blend, indicating that some PEN was incorporated into the interlamellar regions of PET during crystallization. The blend also showed a larger lamellar thickness than pure PET. A reason for the increase in the lamellar thickness might be that the formation of thinner lamellar stacks by secondary crystallization was significantly restricted because of the increased glass-transition temperature. At high crystallization temperatures above 200 °C, the diffusion rates of noncrystallizable components were faster than the growth rates of crystals, with most of the noncrystallizable components escaping from the lamellar stacks. As a result, the blend showed an interfibrillar or interspherulitic morphology. © 2002 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 317–324, 2002

The effects of uniaxial drawing conditions on the orientation of various poly( l -lactide) (PLLA) samples were investigated using Fourier transform infrared dichroism and thermal analysis. The results showed that the orientation in uniaxially stretched PLLA was determined by the drawing rate, drawing temperature, and draw ratio. For the amorphous sample, a higher orientation was obtained at a lower drawing temperature due to the slower chain relaxation. On the other hand, a higher orientation was achieved for the precrystallized samples at a higher drawing temperature due to the larger deformation of spherulites. The hydrolysis tests of PLLA films showed that the rate of hydrolysis was dependent on the degree of orientation as well as the percent crystallinity. After preferential hydrolysis of the amorphous regions, the surface of oriented PLLA samples might be covered by a layer of relatively inactive crystal lamellae, causing a reduction in the rate of hydrolysis.

Poly(vinyl acetate)-TEMPO macroinitiators were synthesized by polymerization of vinyl acetate with benzoyl peroxide followed by termination of the radicals using 2,2,6,6,-tetramethyl-1-piperidinyloxy (TEMPO). Copolymerization of styrene was performed in the presence of the macroinitiator. Due to chain transfer to polymer reactions during the bulk polymerization of vinyl acetate, the copolymerization produced graft copolymers of poly(vinyl acetate) (PVAc) and polystyrene (PS) instead of the corresponding block copolymers. The PVAc-g-PS copolymers had a phase-separated morphology, and the phase separation was realized more completely in the copolymer with the highest VAc content (PS124TP115). PS124TP115 enhanced elongation at break of PVAc/PS blend significantly. The size of the PVAc domains in PS/PVAc/PVAc-g-PS blends decreased and adhesion strength measured by the peel test for hot pressed PS and PVAc sheets with the copolymer inserted in between increased in the order of PS124TP115≫PS145TP110≈PS144TP096≈PS162TP089, indicating that PVAc-g-PS copolymers having similar content of the components were more effective in compatibilizing the PS/PVAc blends.

Poly(vinyl acetate) (PVAc) was added to the crystalline blends of poly(ethylene oxide) (PEO) and poly(L-lactide) (PLLA) (40/60) of higher molecular weights, whereas diblock and triblock poly(ethylene glycol)–poly(L-lactide) copolymers were added to the same blend of moderate molecular weights. The crystallization rate of PLLA of the blend containing PVAc was reduced, as evidenced by X-ray diffraction measurement. A ringed spherulite morphology of PLLA was observed in the PEO/PLLA/PVAc blend, attributed to the presence of twisted lamellae, and the morphology was affected by the amount of PVAc. A steady increase in the elongation at break in the solution blend with an increase in the PVAc content was observed. The melting behavior of PLLA and PEO in the PEO/PLLA/block copolymer blends was not greatly affected by the block copolymer, and the average size of the dispersed PEO domain was not significantly changed by the block copolymer. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3618–3626, 2001

Liquid–liquid (L–L) phase separation and its effects on crystallization in polypropylene (PP)/ethylene–propylene rubber (EPR) blends obtained by melt extrusion were investigated by time-resolved light scattering (TRLS) and optical microscopy. L–L phase separation via spinodal decomposition (SD) was confirmed by TRLS data. After L–L phase separation at 250°C for various durations, blend samples were subjected to a temperature drop to 130°C for isothermal crystallization, and the effects of L–L phase separation on crystallization were investigated. Memory of the L–L phase separation via SD remained for crystallization. The crystallization rate decreased with increasing L–L phase-separated time at 250°C. Slow crystallization for the long L–L phase-separated time could be ascribed to decreasing chain mobility of PP with a decrease in the EPR component in the PP-rich region. The propylene-rich EPR exhibited good affinity with PP, leading to a slow growth of a concentration fluctuation during annealing. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 695–700, 2001

Liquid-liquid (L-L) phase separation and its effects on crystallization in polypropylene (PP)/ethylene-propylene rubber (EPR)/ethylene-α-olefin copolymer (ECP) ternary blends obtained by melt extrusion were investigated by time-resolved light scattering (TR-LS) and optical microscopy. L-L phase separation via spinodal decomposition (SD) was confirmed by TR-LS data. After L-L phase-separation at 250°C for various durations, the blend sample was subjected to temperature-drop to 130°C for isothermal crystallization and the effects of L-L phase separation on crystallization were investigated. Memory of L-L phase separation via SD remained for crystallization. The crystallization rate decreased with increasing L-L phase-separated time at 250°C. Slow crystallization for the long L-L phase-separated time could be ascribed to decrease in chain mobility of PP by decrease in rubbery components in the PP-rich region. The ethylene-octene copolymer exhibited good affinity with PP, leading to a slow growth of a concentration fluctuation during annealing.

Liquid-liquid phase separation and subsequent homogenization during annealing in an extruded poly(ethylene terephthalate) (PET)/poly(ethylene-2,6-naphthalate) (PEN) blend were investigated with time-resolved light scattering and optical microscopy. In the initial stage, the domain structure was developed by demixing via spinodal decomposition. In the later stage, the blend was homogenized by transesterification between the two polyesters. The crystallization rate depended on the sequence distribution of polymer chains, which was determined by the level of transesterification rather than the composition change of separated phases. When the crystallization of PEN preceded that of PET, PEN showed a higher melting point. However, when the crystallization rate of PEN was slower than that of PET, the previously formed PET crystals suppressed the crystallization of PEN, causing the coarse crystalline structure of PEN to have a lower melting point.

Compatibilization of blends of poly(ethylene terephthalate) (PET) and polystyrene with alternating copolymers of maleic anhydride and isobutylene (IM) and its partly phenol substituted product (PIM) has been studied. The characterization techniques applied were dynamic mechanical analysis, differential scanning calorimetry, scanning electron microscopy, and tensile testing. In all compositions studied, morphological observations demonstrated that the addition of approximately 5 wt % of copolymers led to the domain size reduction of dispersants. The PIM copolymer was most effective in reducing the domain size, whereas the IM copolymer was less satisfactory. The blends containing PIM also gave the more enhanced ultimate strength than those of other systems. The noncrystalline PIM copolymers lowered the tensile modulus of the blend as much as 60% even in the polystyrene-rich region and varied linearly with values of quenched PET modulus throughout the compositions, indicating the formation of homogeneous amorphous phase. Based on the experimental observation that the reduced domain size with PIM copolymer, a compatibilization mechanism of the blend with PIM alternating copolymer is proposed and discussed in terms of the interactions between ester groups of PET and PIM (transesterification), and the possible formation of intermediate π-complex between the π-electron deficient aromatic ring of PIM and π-electron rich aromatic ring of PS. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1998–2007, 2000

Aliphatic polyesters have excellent mechanical properties and biodegradability and are well suited to disposable applications. A drawback is that they currently have a high cost. In an effort to reduce their cost, we have prepared blends of an aliphatic polyester with wheat gluten, an inexpensive biodegradable protein. Plasticizers such as low molecular weight polyols were used in formulations to enhance the processability of the gluten. The resulting biodegradable gluten-based plastics demonstrate good physical and thermal properties. For the gluten granules-based blends, a droplet-like structure was obtained as observed in filler–polymer systems. On the other hand, due to the rheological characteristics of the plasticized gluten, a deformed fine morphology was observed in the plasticized gluten-based blends.

Despite progress in the development of biodegradable polyesters, little attention has been given to aliphatic/aromatic copolyesters. Therefore, a series of such copolyesters has been synthesized by polycondensation of succinic acid (SA), dimethyl terephthalate (DMT) and 1,4-butanediol (BD), and their material characteristics and biodegradability have been examined. The chemical composition of the aliphatic/aromatic copolyesters strongly influences the material characteristics and biodegradability. For the copolyesters with a DMT–BD mole fraction of less than 0.2, an optimum between physical properties and biodegradability seems attainable. © 1999 Society of Chemical Industry

Biodegradability of poly(3-hydroxybutyrate) (PHB) was determined by the modified Sturm test utilizing, activated sludge, or synthetic sludge and the result was more reproducible when the activated sludge was used as the microbial source. As PHB was blended with miscible poly(ethylene-co-85 wt% vinyl acetate) (EVA85), biodegradability of PHB was drastically reduced with the addition of EVA85. On the other hand, the biodegradation rate of the immiscible PHB/poly(ethylene-co-70 wt% vinyl acetate) (EVA70) blend was decreased gradually with an increase in the EVA70 content. Almost same biodegradation behavior was observed both for the PHB/EVA85 blend prepared by hot pressing of precipitation from chloroform solution into hexane and for the blend obtained by chloroform solvent casting. However, biodegradability of the PHB/poly(ethylene oxide) (PEO) blend was decreased rather slowly with an increase in the PEO content, even though it was a miscible blend.

The liquid–liquid (L–L) phase separation and its effect on crystallization in polypropylene (PP)/ethylene–propylene–rubber (EPR) blend obtained by melt extrusion were investigated by time-resolved light scattering (TR-LS), optical microscope and small-angle X-ray scattering (SAXS). The existence of the lower critical solution temperature (LCST) was found by the kinetic analysis of the L–L phase separation, that is, the apparent diffusion coefficient of spinodal decomposition (SD), obtained by the TR-LS, decreased with increasing temperature. The L–L phase-separated specimen at 190°C for various time periods was subjected to a temperature-drop to 130°C for the isothermal crystallization and then investigated effect of L–L phase separation on crystallization. Memory of L–L phase separation via SD remained even after crystallization and crystallization proceeded only in PP-rich phases. The crystallization rate decreased with increasing L–L phase-separated time at 190°C. The rapid crystallization for short L–L phase-separated time could be ascribed to the elevation of chain mobility of PP by relatively higher amounts of EPR in PP-rich phases. The amount of EPR between PP lamellae in PP-rich phases was quantified using the correlation function, which is given by the fourier transform of the SAXS intensity.

Although progress has been made in the study of biodegradable polyesters, little attention was given to aliphatic/alicyclic copolyesters. For this reason, we have undertaken systematic studies on the aliphatic/alicyclic copolyesters. As a first step in our research, we have presented the material characteristics (e.g., thermal and mechanical properties) and the biodegradability in different biological environments for a series of the aliphatic/alicyclic copolyesters that were synthesized by polycondensation of succinic acid, 1,4-butanediol, and 1,4-cyclohexanedimethanol. The chemical composition of the aliphatic/alicyclic copolyesters plays an important role in controlling the material characteristics and biodegradability. For the copolyesters with a mole fraction of succinic acid-1,4-cyclohexanedimethanol

The effects of uniaxial drawing conditions on the orientation of aliphatic copolyester films were investigated by using both Fourier transform infrared-attenuated total reflection (FTIR-ATR) dichroism and wide angle X-ray diffraction (WAXD) methods. The results showed that orientation in uniaxially drawn films was determined by the drawing rate and drawing temperature. At higher drawing rates and higher drawing temperatures, higher orientation was obtained due to a large deformation of spherulites. The WAXD patterns of drawn films exhibited the preferential orientation of lamellar crystallites. The results of microbial degradation indicated that development of crystalline orientation evidently depressed biodegradability of samples. Video microscopy observations revealed that the degree of orientation played a dominant role in determining the rate of surface erosion.

Blends of a polyester hot melt resin and a poly-α-olefin hot melt resin were modified using the reactive compounding technique. The effects of the compatibilizers were evaluated by studying the mechanical properties, the morphology, and the thermal properties of the modified blends. A pronounced compatibilizing effect was obtained with dual compatibilizers composed of maleated polypropylene and poly[methylene (phenylene isocyanate)] (PMPI). The addition of 1 phr of PMPI was sufficient to improve the elongation and tensile strength. From the results, it is anticipated that PMPI can be used as an efficient coupler to enhance the compatibility of immiscible polyester/polyolefin blends. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40232.

Oxygen plasma treatment was used to introduce functional groups on the surface of polyacrylonitrile-based carbon fibers. The fiber surface was examined by X-ray photoelectron spectroscopy after treatment. The amount of functional groups on the fiber surface initially increased with increasing treatment time up to 2 min, thereafter remaining constant. The variation of surface energy with plasma treatment showed a similar trend. The plasma treatment affected the surface area and the mechanical properties of carbon fibers. The surface area increased but the mechanical properties decreased with increasing treatment times. The plasma treatment also changed the morphology of the fiber surface.