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PMMA nanocomposites based on the synthetic smectite were prepared and characterized. The synthetic smectites, STN and SPN, were effectively hybridized in the PMMA matrix, as confirmed by X-ray diffraction patterns and by transmission electron microscopy, and optical and thermal properties were measured. The morphologies of PMMA nanocomposite films, containing 1–9 wt% with respect to synthetic smectite, were defined as exfoliated-immiscible and exfoliated-intercalated nanocompostites for CHT and CHP series, respectively. The optical properties, such as haze and UV transmittance, were maintained for organoclay loading of 9 wt% for CHP series. Thermal stability evaluated by TGA showed a small increase in the maximum decomposition temperature (T d); however, the coefficient of thermal expansion (CTE) dramatically decreased with the amount of organoclay content. The storage modulus and loss modulus increased with the weight fraction of organoclay.

Biodegradable ultrafine poly(butylene succinate) (PBS) fibers were continuously electrospun for the first time from PBS solutions in chloroform (CF)/2-chloroethanol (CE) (7/3, w/w), CF/CE (6/4, w/w), dichloromethane (DM)/CE (7/3, w/w), DM/CE (6/4, w/w), and CF/3-chloro-1-propanol (9/1, w/w). These mixed solvents had an appropriate evaporation rate for the continuous electrospinning of PBS. The ultrafine PBS fibers had very high crystallinity and their average diameters were in the range of 125–315 nm. The annealed ultrafine PBS fibers exhibited a lamellar stack morphology containing crystalline and amorphous layers.

Poly(butylene succinate) (PBS) and PBS-based ionomers (PBSi's) with 0.3 and 1.2 mol-% of sodium sulfonated succinate unit were synthesized. The existence of ionic aggregates in the ionomer matrices was indicated by melt viscosity and glass transition data. It seems that the ionic aggregates have two opposing roles in crystallization: one is the induction of nucleation and the other is the interference with lamellar growth. Because of these two contrary effects, the crystallization behavior of the ionomers exhibited measurably different cooling rate-dependencies than that of the parent PBS. The rate varied distinctly with ionic content.

Maximum temperature during the thermophilic phase and moisture content were controlled in the course of composting to examine the effects of these composting conditions on the quality of the compost used for the evaluation of the biodegradability of plastics. The moisture content during composting was controlled at 65%, while keeping the maximum temperature below 46°C, 58°C and 70°C, respectively. In turn, the maximum temperature was controlled to be below 58°C, while maintaining the moisture content at 45%, 55% and 65% respectively. The number of microbial cells was examined in the five compost samples thus prepared. Biodegradation of cellulose, polycaprolactone and poly(butylene succinate-co-butylene adipate) was conducted in the five compost samples, and the consistency and reproducibility of the test results were explored.

To evaluate the potential of polyester-based ionomers as biomaterials, we have characterized them in terms of crystallization behavior, degradation, and in-vitro cellular interactions. The polymers used are poly(butylene succinate)-based ionomers (PBSis) with 1 to 5 mol-% dimethyl 5-sodium sulfoisophthalate. Even a few incorporated ionic groups significantly decreases the folding surface energy, indicating that folding into crystalline lamellae is more difficult for chains restricted by ionic aggregates. Transmission electron microscopy (TEM) does not reveal any distinct aggregation of ionic clusters following hydrolytic degradation, which suggests that the physical crosslinkage due to ionic interactions is vulnerable to hydrolysis. The in-vitro cellular interactions of polyester-based ionomers is assessed by the culture of human dermal fibroblasts with PBSi extracts or in direct contact with the PBSi films. Cells on PBSi films and in their extracts exhibit appropriate specific growth rates and normal metabolic function regardless of the incorporated ionic content compared with poly[(D,L-lactic acid)-co-(glycolic acid)] (75:25, PLGA), which is well known to be biocompatible. The cells growing on PBSi films spread to a sufficient extent, displaying relatively active filopodial growth, as compared to that of parent PBS. These results suggest that the conspicuous topology and hydrophilic nature of the ionomer surface affect cellular interactions, and that this ionomer therefore has potential applications as a biomaterial.

A series of conductive polycarbonate films (CPCFs) were prepared by spin coating with an ethanol-based coating solution comprised of dodecylbenzenesulfonic acid-doped poly(3,4-ethylenedioxythiophene) (PEDOT)/sorbitol. The variation of CPCF surface resistivity was then measured as a function of temperature. CPCF surface resistivity decreased as sorbitol content increased, with the minimum values in the temperature range 175–185 °C. Furthermore, the CPCF-1.6 exhibited significantly improved thermal stability with respect to surface resistivity even at 175 °C. FT-IR analysis indicated that, after thermal treatment, hydrogen bonds arising from the hydroxy groups of sorbitol or hydroxypropyl cellulose and carbonyl groups of polycarbonate were established. The combination of surface resistivity data and FT-IR analysis suggests that the introduction of sorbitol accompanied with thermal treatment allows the PEDOT chains to undergo favorable inter-chain interactions leading to charge transfer and physical cross-linkage via hydrogen bonding.

The crystallization kinetics and morphology of PEN/PET copolyesters were investigated using differential scanning calorimetry (DSC), time-resolved small-angle X-ray scattering (TR-SAXS), and transmission electron microscopy (TEM). The Avrami exponents obtained using DSC were approximately 3 for homo PEN and 4 for all the copolyesters. The 3-parameter Avrami model was successfully fitted to the invariants with respect to the time obtained from TR-SAXS, and the exponent values were similar to those obtained from DSC. Moreover, the Avrami rate constants obtained from TR-SAXS showed marked temperature-sensitive decreases in all samples, like those obtained from DSC. This indicates that not only could changes in morphological parameters be obtained from the analysis of TR-SAXS data but also crystallization kinetics. The changes in the morphological parameters determined from the SAXS data indicate that the minor components, dimethyl terephthalate (DMT) segments, are rejected into the amorphous phase during crystallization. In the TEM study, copolyesters crystallized at temperature above 240 °C grew into both the α- and β-form, although 240 °C is the optimum condition for the β-form crystal. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 805–816, 2005

We report an important and useful method for preparing ω-sulfonated polystyrene-stabilized cadmium sulfide (CdS) nanoclusters. The ω-sulfonated polystyrene (M n = 5000 g/mol) was prepared successfully through chain-end sulfonation of poly(styryl)lithium using 1,3-propanesultone; the resulting polymer was used successfully as a polymeric stabilizing agent for the preparation of semiconductor CdS nanoclusters by reduction of cadmium acetate in a mixture of toluene and methanol (9∶1, v/v). The nanoclusters that formed were characterized by a combination of transmission electron microscopy, X-ray diffraction, and UV/Vis spectroscopic analysis. The ω-sulfonated polystyrene-stabilized CdS nanoclusters synthesized in this study exhibited the cubic phase (zinc-blende phase) structure in the range of 2∼8 nm.

A series of poly(trimethylene terephthalate) (PTT) nanocomposites, containing an organically modified montmorillonite (C 12 PPh-MMT), were prepared by in situ intercalation polymerization of dimethyl terephthalate (DMT) and 1,3-propanediol (PDO). The PTT nanocomposites were melt-spun at different organoclay contents and different draw ratios (DRs) to produce monofilaments. The nanocomposites were characterized by X-ray diffraction, electron microscopy, universal tensile testing, differential scanning calorimetry and thermogravimetric analysis. Some of the clay particles appeared well dispersed within the PTT matrix, while others were found to agglomerate with a size greater than 10 nm. The addition of a small amount of C 12 PPh-MMT was sufficient to improve the thermo-mechanical properties of the PTT hybrid fibers. Both the thermal stability and the tensile strength increased with increasing clay content at DR=1. As the DR was increased from 1 to 9, the ultimate tensile strength of the hybrid fibers decreased, while the initial modulus remained constant.

Hyaluronan (HA) is one of the polysaccharides that is found widely in connective tissue of mammals, and it has no sulfate group and high molecular weight in comparison with other glycosaminoglycans. Glycosaminoglycans are deeply concerned with the manifestation of biofunctions not only by their physical properties but also by physiological ones. In this study, sulfated HA (S-HA) with various degrees of sulfate substitution and high molecular weight will be synthesized in order to give HA new biological functions. Moreover, the effect of HA and S-HA on cell proliferation of human epidermal keratinocytes in vitro will be discussed. HA did not affect lag phase, but growth rate (metabolic turnover) of the cell in a logarithmic growth phase which was controlled by the molecular weight of HA. S-HA stimulated the cell proliferation in the low concentration region under 1 μg/ml. While it inhibited the cell proliferation in the high concentration region over 10 μg/ml. It strongly suppressed the cell proliferation in the logarithmic growth metaphase. These facts were considered to be caused by the change of the cell-matrix and/or cell–cell interactions. Copyright © 2004 John Wiley & Sons, Ltd.

We report new application fields of telechelic polymers synthesized via chain-end functionalizations of living polymers readily prepared from anionic polymerizations using lithium naphthalenide. The molecular weights of functionalized polymers were controlled in the range of 2000–50,000 g/mol. The functionalization yields were over 98 mol% on the basis of the results by 1H NMR analysis. Among several telechelic polymers, dilithium α,ω-disulfonated polystyrene could be used as an efficient compatibilizer to control the morphologies of the polystyrene/nylon 6 or the polystyrene/poly(ethylene terephthalate) blend systems through the ionic-dipole interaction mechanism. All telechelic polymers carrying hydoxylate, carboxylate, sulfonate, and thiol groups were successfully used as the polymer stabilizers for preparation of nano-sized cadmium sulfide (CdS) semiconductor in the range of 5–30 nm.

A series of polyester-based ionomers containing dimethyl 5-sulfoisophthalate sodium salt (DMSI) with up to 5 mol-% diacid units was synthesized by two-step polycondensation. Furthermore a polylactic acid (PLA) was modified by introducing poly(ethylene-co-methacrylic acid) ionomers with different ion groups, such as Na, Li, and Zn, using the melt blending method. This review examines the effect of the ionic group on the dynamic mechanical properties, melt rheology, crystallization behavior, degradation behavior, and biocompatibility with human dermal cells, as well as the nucleating effect of poly(ethylene-co-methacrylic acid) ionomer in PLA.

The crystallization behavior of a poly(butylene succinate)-based ionomer (PBSi) was analyzed by morphological observations and synchrotron small-angle X-ray scattering (SAXS) experiments. The spherulitic morphology of PBSi is composed of irregular lamellae propagating outwards from the center with ionic clusters isolated from the crystalline lamellae. Synchrotron radiation SAXS profiles revealed that the re-crystallization during heating process was effectively retarded with increasing ionic content, suggesting that the presence of ion aggregates affects the extent of diffusion of chains towards crystallization.

Poly(3,4-ethylenedioxythiophene) (PEDOT) nanoparticles with enhanced conductivity and processability were prepared by oxidative polymerization in dodecylbenzne sulfonic acid (DBSA) micellar solutions. DBSA was used to act simultaneously as a surfactant to form micelles and as a doping agent. Monomers of EDOT, which has extremely low solubility to water, were easily solubilized in aqueous DBSA micellar solution. The effects of DBSA on the resulting PEDOT structure, morphology and electrical property were investigated when DBSA was used in combination with two different oxidants, i.e., iron(III) chloride and ammonium persulfate. The electrical conductivity was varied with the polymerization conditions, and it was relatively high up to 50 S/cm. The morphology of the particles, determined by Field emission scanning electron microscopy (FE-SEM), appeared to be quite spherical and their sizes ranged from 35 to 100 nm in diameter. The colloidal properties of the PEDOT nanoparticles were also investigated.

Nanocomposites of poly(ethylene terephthalate) (PET) with C12PPh–MMT as an organoclay were synthesized by using the in situ interlayer polymerization approach. The PET nanocomposites were melt-spun at different organoclay contents and different draw ratios to produce monofilaments. The thermo-mechanical properties and the morphologies of the PET nanocomposites were examined by using a differential scanning calorimeter, a thermogravimetric analyzer, a wide angle X-ray diffactometer, scanning and transmission electron microscopes, and a universal tensile machine. Some of the clay particles were well dispersed in the PET matrix, and some of them were agglomerated at a size level of greater than approximately 10 nm. The thermal stability and the tensile mechanical properties of the PET hybrid fibers increased with increasing clay content at a DR=1. However, the values of the ultimate tensile strength and the initial modulus of the hybrid fibers decreased markedly with increasing DR from 1 to 16.

We have prepared poly(ethylene terephthalate) (PET) nanocomposites filled with two different types of fumed silicas, hydrophilic (FS) and hydrophobic (MFS) silicas of 7-nm diameter, byin situ polymerization. We then investigated the morphological changes, rheological properties, crystallization behavior, and mechanical properties of the PET nanocomposites. Transmission electron microscopy (TEM) images indicate that the dispersibility of the fumed silica was improved effectively byin situ polymerization; in particular, MFS had better dispersibility than FS on the non-polar PET polymer. The crystallization behavior of the nanocomposites revealed a peculiar tendency: all the fillers acted as retarding agents for the crystallization of the PET nanocomposites. The incorporation of fumed silicas increased the intrinsic viscosities (IV) of the PET matrix, and the strong particleparticle interactions of the filler led to an increased melt viscosity. Additionally, the mechanical properties, toughness, and modulus of the nanocomposites all increased, even at low filler content.

Biodegradability of cellulose fabrics was evaluated by use of a soil burial test, an activated sewage sludge test, and an enzyme hydrolysis. Surface changes after biodegradation were observed by optical microscopy. From X-ray diffraction analysis (XRD), changes in the crystallinities and the internal structures as a result of degradation were also investigated. It was shown that biodegradability decreased in the following order: rayon > cotton ≫ acetate. Rayon fibers, which have a low crystallinity and a low degree of orientation, showed the highest biodegradability in most cases. However, in spite of its low crystallinity, acetate fibers exhibited very low biodegradability, probably because of the presence of hydrophobic groups in its structure. On the other hand, linen showed an inconsistent behavior in that it had the highest biodegradability in the soil burial test, but a lower biodegradability than that of cotton in the activated sewage sludge test. XRD analysis revealed that there was a slight increase in the crystallinity of linen, cotton, and rayon fabrics at the initial stage, but a continuous decrease thereafter. From the correlation analysis, it was revealed that the biodegradability of cellulose fabrics was closely related to the moisture regain of the fibers, which reflects the hydrophilicity and internal structure of the fibers at the same time. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 248–253, 2004

Transient structure and crystallization behaviors in cold-drawn PET fibers were studied by synchrotron wide-angle X-ray diffraction, IR spectroscopy, and thermomechanical analysis. As-spun PET fibers were mechanically cold-drawn up to the breaking point, and those stretched ones beyond the strain hardening point in the stress−strain curve exhibited the transient layer structure. Evidence suggesting the tilted PET chains within the transient layer structure, and therefore the smectic C mesophase, was discussed. The tilt angle of the chains within the layer was 6° against the fiber axis. The tilt angle, however, decreased rapidly with the crystallization. Results of X-ray diffraction, IR absorbance, and thermomechanical analysis suggested two-stage crystallization in oriented PET chains. Bundles of highly oriented chains including the mesophase were responsible for the first stage crystallization (80−100 °C), but those of less ordered or nonoriented chains were for the second stage crystallization beyond 14...

A series of poly(butylene succinate) ionomers (PBSi) containing 5-sodium sulfoisophthalate units were prepared by bulk polymerization of succinic acid and 1,4-butanediol in the presence of dimethyl 5-sulfoisophthalate sodium salt (DMSI) up to 5 mol% of diacid monomer. Conspicuous variation of the storage modulus for PBSi was observed, depending on the content of DMSI. The increasing rate of cluster T g was lower compared to those of amorphous polymer-based ionomers. These results were probably due to the lower clustering ability of semi-crystalline PBSi as compared with amorphous-based ionomers. Non-contact atomic force microscopy confirmed that the size of PBSi-3 clusters was about 40∼50 nm, demonstrating that the clusters were aggregated. Melt rheological analysis was carried out to investigate the effects of ionic groups on the rheological properties as a function of temperature or shear force in the molten state. The melt viscosities of PBSi showed higher values than the parent PBS up to about 190 °C, while with further increasing temperature a falling inflection region of melt viscosity was observed. It was suggested that the relaxation of PBSi chains was due to the thermal dissociation of ionic aggregates.

The crystallization behavior and morphology of poly(ethylene 2,6-naphthalte) (PEN) were investigated by means of differential scanning calorimetry (DSC), polarized optical microscopy (POM) and transmission electron microscopy (TEM). POM results revealed that PEN crystallized at 240 °C shows the coexistence of α and β-form spherulite morphology with different growth rates. In particular, when PEN crystallized at 250 °C, the morphology of spherulites showed a squeezed peanut shape. The Avrami exponents decreased from 3 to 2.8 above the crystallization temperature of 220 °C, indicating a decrease in growth dimension. Analysis from the secondary nucleation theory suggests that PEN crystallized at 240 °C has crystals with both regime I and regime II. In TEM observation, the ultra-thin PEN film crystallized at 200 °C showed the spherulitic texture with characteristic diffractions of α-form, while PEN crystallized at 240 °C generated an axialite structure with only β-form diffraction patterns. In addition, despite a long crystallization time of 24 h, amorphous regions were also observed in the same specimen. It was inferred that the initiation of PEN at 240 °C generates only β-form crystals from axialite structures.

The effect of surface hydrophilicity was induced from the amide units in the polyesteramide. The surface energies and compositions of the polyesteramides were studied by employing contact angle and interfacial tension measurements and ESCA analysis. Biodegradability was evaluated form various methods including activated sludge test, enzyme hydrolysis, and soil burial test, which determine the amount of evolved CO2, weight loss, and TOC values, respectively. It was found that the introduction of amide groups to the aliphatic polyester improved the biodegradability, although the increase of biodegradation rate was not directly proportional to the amide content. The biodegradability of aliphatic polyesters increased with the addition of amide functionality. Therefore, it can be concluded that the addition of appropriate contents of hydrophile enhanced the biodegradability of aliphatic polyesters as well as their physical properties. Also, the experimental results revealed the relation between hydrophilicity and biodegradability of polyesteramides. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2708–2714, 2003

Intercalated nanocomposites with poly(butylene terephthalate) (PBT) incorporated between the montmorillonite layers were synthesized from dimethyl terephthalate and 1,4-butane diol by using an in situ interlayer polymerization. The PBT nanocomposites were melt-spun at different organoclay contents to produce monofilaments. The samples were characterized by using wide angle X-ray diffraction, electron microscopy, thermal analysis, and tensile testing. The extent of the clay layer in the PBT was confirmed by using X-ray diffraction and electron microscopy, and the clay layer was found to be highly dispersed on a nanometer scale. The addition of only a small amount of organoclay was enough to improve the thermo-mechanical properties of the PBT hybrid fibers. The hybrids were extruded with various draw ratios (DRs) to examine the tensile mechanical property of the fibers. At DR=1, the ultimate tensile strength of the hybrid fibers increased with the addition of clay up to a critical content and then decreased. However, the initial modulus monotonically increased with increasing amount of organoclay in the PBT matrix. When the DR was increased from 1 to 6, for example, the strength and the initial modulus values of the hybrids containing 3 wt% organoclay decreased linearly.

Poly(vinyl acetate-co-vinyl alcohol) copolymers [P(VAc-co-VA)] were prepared by acidic hydrolysis of poly(vinyl acetate) (PVAc) at various reaction time, and the degree of hydrolysis was analyzed by 13C nuclear magnetic resonance spectroscopy (NMR). Blends of poly( l -lactic acid) (PLA) and P(VAc-co-VA) were prepared by a solvent casting method using chloroform as a co-solvent. The PLA/PVAc blends exhibited a single glass transition over the entire composition range, indicating that the blends were miscible systems. On the contrary, for the blends with even 10% hydrolyzed PVAc copolymer, the phase separation and double glass transition were observed. With increasing neat PVAc contents, the heat of fusion decreased and the melting peaks shifted to lower temperature. The interaction parameter indicated negative values for up to 10% hydrolyzed samples, but positive values at more than 20% hydrolyzed one. Small angle X-ray scattering analysis revealed that the long period and the amorphous layer thickness increased with PVAc composition, suggesting that a considerable amount of PVAc component located in the interlamellar region. Polarized optical microscopy showed that the texture of spherulites became rougher on increasing the PVAc content. In the case of P(VAc-co-VA) copolymer, the intensity of polarized light decreased significantly, indicating that P(VAc-co-VA) component seemed to be expelled out of the interfibrillar regions. Scanning electron microscopy analysis revealed that the significant phase separation occurred with increasing the degree of hydrolysis. In the case of 70/30 blend of PLA and P(VAc-co-VA) with 30 mol% vinyl alcohol, the P(VAc-co-VA) copolymer formed the regular domains with a size of about 10 μm.

The effect of orientation in the amorphous and crystalline region on the biodegradability of linear and star-shaped Poly(glycolide-co-e-caprolactone)(PGCL) was studied in terms of the crystalline orientation, the crystallinity and thermal properties. Microstructual changes during hydrolysis of the drawn linear and star-shaped PGCL films were investigated using the conventional wide-angle X-ray diffraction equipped a fiber specimen attachment. The drawn star-shaped PGCL showed higher degradation rate than the drawn linear shaped and the degradation decreased with increasing draw ratio. During hydrolysis, the crystallinity for all the samples increased but the crystalline orientation decreased. In particular, the decrement of the crystalline orientation for star-shaped PGCL was higher than that of linear PGCL.

Seeds of red pepper and tomato were sowed and cultivated in a soil blended with powdery poly(l-lactide) (PLLA), and poly(butylene succinate) (PBS). PBS depressed the growth of the two plants significantly even at a concentration as low as 5%, whereas PLLA up to 35% affected negligibly or even boosted the growth of the two plants. pH and number of microbial cells in the soil after 80 days of cultivation were almost the same independently whether the soil was blended with the two polymers or not. In contrast, the molecular weight of PBS decreased much faster than that of PLLA. Because succinic acid and 1,4-butane diol, from which PBS was synthesized, exhibited toxicity to both plant and animal cells to retard the germination rate of young radish seeds and to deform the morphology of HeLa cells significantly [1], the monomers and the oligomers produced from the PBS degradation should have a detrimental influence on the growth of the two plants.

Rapidly biodegradable and feasible poly(butylene adipate) ionomers (PBAi) were synthesized using dimethyl 5-sulfoisophthalate sodium salt (DMSI) up to 5 mol% of diacid monomer. Spectroscopically determined ionic contents of the polymers corresponded well to the feed compositions. Melt rheology experiments displayed the relaxation of ion clusters in PBA ionomers containing 3–5 mol% DMSI over the temperature range of 150–200 °C. The melting point depression in the ionomers was less than 1 K per mol% of DMSI, comparable to the most aliphatic co-polyesters. On the other hand, substantial decrease in enthalpy of fusion was observed at 3–5 mol% of ion content, indicating that crystallization is seriously retarded by the ionic interaction. It was found that PBA ionomers, despite the low molecular weight, exhibited acceptable tensile properties ascribable to chain extension effect due to the ionic interactions. Most importantly, the hydrolytic degradation of the ionomers was drastically accelerated compared to PBA homopolymer because the presence of ionic moieties reduced the crystallinity and allowed easier moisture penetration, and thus improved hydrolytic susceptibility.

A series of poly(oxyethylene-block-esteramide)s (PASHs) containing p-aminobenzoic acid units were prepared by bulk polymerization of N, N � -bis( p-ethoxycarbonylphenyl) sebacamide and mixed diols of 1,6-hexanediol and poly(ethylene glycol) (PEG, MW 600, up to 34 mol%). The poly(oxyethylene-block-esteramide)s exhibited the inherent viscosity ranging from 0.61 to 0.87 dL g −1 while the parent poly(ester-amide) yielded an inherent viscosity of 0.41 dL g −1 ,w hich isattributable to chain extension and homogeneity of reaction mixture in the presence of PEG. The parent poly(ester-amide) showed relatively fast crystallization and high Tg for its alternating arrangement of ester- amide sequence, resulting in extremely brittle characteristics. However, the glass transition temperatures, Tg ,o f the poly(oxyethylene-block-esteramide)s containing 13-16 mol% of PEG were found in the range 31- 45 ◦ Ca nddemon- strated greatly improved mechanical properties. The storage modulus in ambient temperature was ca. 1300-1400 MPa, and the tensile strength was measured 40-85 MPa. From the dynamic mechanical analysis it was also found that stor- age modulus at rubbery plateau region increased as PEG was introduced up to 16 mol%, indicating a good dimensional stability above Tg. KE YW ORDS Poly(ester-amide) / Poly(oxyethylene-block-esteramide)s / Hard Segment / Soft Seg- ment / Dimensional Stability / Dynamic Mechanical Properties /

Nanoparticles of electroconductive polymers were prepared in micellar solution as a polymerization medium to overcome the poor processability of electroconductive polymers. The morphologies of particles were studied through SEM and electrical conductivities of pellets formed with nanoparticles were measured by four-probe apparatus. Among many other electroconductive polymers, nanoparticles of polyaniline and poly(3,4-ethylenedioxythiophene) were prepared in anionic sodium dodecyl sulfate and dodecylbensen sulfonic acid micellar solutions. The sizes and shapes of particles were similar to those of micelles. The electrical conductivities of pellets formed with nanoparticles were 20 and 50 S/cm depending upon the polymerization conditions, which are higher values than those of pellets formed with particles prepared in bulk solutions.

PET nanocomposites filled with fumed silicas were prepared via direct melt compounding method at various mixing conditions such as filler type and filler content. Some fumed silicas were pre-treated to improve the wettability and dispersibility, and principal characterizations were performed to investigate the effects of nano fumed silicas on polymer matrix. Hydrophobic fumed silica (M-FS), which has the similar contact angles of water with neat PET, acted as the best reinforcement for the thermal stability and mechanical properties of PET nanocomposite, and FE-SEM images also showed that M-FS was uniformly dispersed into matrix and had good wettability. But, some filler (O-FS) had low dispersibility and caused the deterioration of mechanical properties. Besides, the results of DSC revealed the nucleation effect of all fillers in polymer matrix, and PET nanocomposite filled with hydrophilic fumed silica (FS) showed markedly the characteristic dynamic rheological properties such as shear thinning behavior at very low frequencies and the decrease of viscosity.

Carbon black-filled high-density polyethylene (HDPE)/ethylene ethylacrylate copolymer (EEA) blends were prepared and the effect of crosslinking of the blends on the positive temperature coefficient (PTC) stability was investigated. By irradiation and silane-crosslinking methods, crosslinked composites with various degrees of crosslinking were obtained. Crosslinking of the matrix polymer led to the disappearance of the negative temperature coefficient (NTC) phenomenon. Also, the PTC intensity increased with an increasing degree of crosslinking. The PTC stability of silane-crosslinked samples was notably improved at heat cycles of 140°C. This was sufficiently improved by both the silane- and radiation-crosslinking methods when they were treated at 85°C. Therefore, the limiting temperature of self-regulating heat is about 85°C. Both radiation- and silane-crosslinked samples are thought to be of use to the industry.

The mixtures of non-conjugated dienes, 4-methyl-1,4-hexadiene and 5-methyl-1,4-hexadiene (MHD), were successfully synthesized by the reaction of isoprene with ethylene using Fe(III)-based catalyst in toluene. The conversion was over 96 mol% on the basis of the initial amount of isoprene used. The production yield for MHD was nearly 50 mol%, the other was polyisoprene. The mixtures were successfully copolymerized with ethylene by using zirconium-based metallocenes. The products were characterized by the combinations of gas chromatography, high temperature gel permeation chromatography,1H NMR,13C NMR, high temperature1H NMR, UV/Visible spectroscopy, and differential scanning calorimetry. It was found that 5-methyl-1,4-hexadiene was active enough to be incorporated into the copolymer chain but the corresponding isomeric material, 4-methyl-1,4-hexadiene, was inactive in metallocene-catalyzed copolymerizations. Specifically, in the zirconocene-catalyzed copolymerizations of ethylene with MHD,ansa-structure catalysts seem to be more efficient than non-bridged type zirconocene. The degree of incorporation of MHD in the resulting copolymers was able to be controlled by the amount of non-conjugated dienes used initially.

The structure development and dynamic properties of fibers produced by high-speed spinning of P(EN-ET) random copolymers were investigated. The as-spun fibers were found to remain amorphous up to the spinning speed of 1500 m/min, and subsequent increases in speed resulted in the crystalline domains containing primarilyα crystalline modification of PEN. Theβ modification was not found up to spinning speeds of 4500 m/min. On the other hand, annealing of constrained fibers spun at the 2100 m/min at 180, 200, and 240°C exhibitedβ-form crystalline structure, while the annealed fibers spun in 600–1500 m/min range exhibited dominantlyα-form. Howeverβ-form crystals disappeared above the spinning speed of 3000 m/min. With increasing spinning speeds from 600 to 4500 m/min, the storage modulus of as-spun fibers increased continuously and reached a value of about 10.4 Gpa at room temperature. The tanδ curves showed theα-relaxation peak at about 155–165°C, which is considered to correspond to the glass transition. Theα-relaxation peaks became smaller and broader, and shift to higher temperatures as the spinning speed increases, meaning that molecular mobility in the amorphous region is restricted by increased crystalline domain.

Chemical oxidative polymerization of aniline was performed in a micellar solution of dodecylbenzene sulfonic acid (DBSA, anionic surfactant) to obtain conductive nanoparticles with enhanced thermal stability and processability. DBSA was used to play both the roles of surfactant and dopant. The polymerization kinetics and optimum polymerization conditions were determined by UV–VIS spectra. The optimum molar ratio of oxidant to aniline was 0.5 and DBSA content was the most important factor in the formation of polyaniline (PANI) salt. The polymerization rate was increased with increasing DBSA concentration. The reaction model was proposed on the basis of the roles of DBSA. The electrical conductivity varied with the molar ratio of DBSA to aniline and the highest conductivity of particles was 24 S/cm. The layered structure due to PANI backbone separated by long alkyl chains of DBSA was observed and it seems to facilitate the electrical conduction. The doping level of particle was fairly high and was dependent on the preparative conditions. The average size of the PANI particles determined by Guinier plot of small-angle X-ray scattering (SAXS) measurement was 20–30 nm, which was well coincidence with scanning electron microscopy (SEM) results

Blends of poly(L-lactic acid) (PLA) and poly(butylene succinate) (PBS) were prepared in various compositions via melt mixing, and the morphological changes were investigated with differential scanning calorimetry and synchrotron wide-angle and small-angle X-ray scattering techniques at a heating rate of 10 °C/min. Differential scanning calorimetry thermograms of PLA/PBS blends showed two distinct melting peaks over the entire composition range. The exothermal peak for PLA shifted significantly to a lower temperature and overlapped with that of PBS around 100 °C. A depression of the melting point of the PLA component via blending was observed. The synchrotron wide-angle X-ray scattering during heating revealed that there was no cocrystallization or crystal modification via blending. The synchrotron small-angle X-ray scattering data showed that well-defined double-scattering peaks (or peaks with a clear scattering shoulder) appeared during crystallization, indicating that this system possessed dual lamellar stacks. These peaks were deconvoluted into two components with a peak separation computer program, and then the morphological parameters of each component were obtained by means of the correlation function. The long period and average lamellar thickness of the two components before melting decreased with an increasing content of the other polymer component. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1931–1939, 2002

Complete exfoliation of montmorillonite during Ti-based Ziegler-Natta polymerization of ethylene has been successfully carried out by using montmorillonite (MMT-OH) modified with intercalation agents containing hydroxy groups. Hydroxyl groups in intercalation agents offer facile reactive sites for anchor ing catalysts in between silicate layers. Comparison of exfoliation characteristics between MMT-OH and non-intercalated montmorillonite showed that the feasibility of exfoliation during ethylene polymerization was highly dependent on the catalyst fixation method.

Poly(butylene succinate-co-butylene 2-methyl succinate) (PBSMS) random copolymers were synthesized with various comonomer compositions and their crystallization behaviour and morphology were investigated by differential scanning calorimeter, small angle X-ray scattering and polarized optical microscopy. The equilibrium melting temperature obtained by the Hoffman–Weeks plot significantly decreased with increasing comonomer concentration containing methyl side-groups. Spherulitic growth rates were strongly dependent on comonomer concentration and were analyzed using the Lauritzen–Hoffman kinetic theory. The surface free energy (σσe) dramatically decreased with comonomer contents. From analysis of the SAXS data, the dependence of the lamellar thickness on crystallization temperature decreased with increasing comonomer concentration. © 2002 Society of Chemical Industry

Poly(ester-co-amides), PBSe random copolymers, were prepared by polycondensation of sebacic acid and 1,4-butanediol, introducing 1,4-butanediamine as comonomer. The homopolymer was semi-crystalline with T m of 65 °C. When the amide content was over 10%, two melting endotherms were observed and their melting enthalpies decreased significantly. WAXD results also showed a decrease of crystallinity with increasing amide content. Poly(ester-co-amides) had intramolecular and intermolecular hydrogen bonding, which was conformed by FT-IR. The degradability of the PBSe series increased with the amide content. Quantitative FT-IR analysis shows that the areas of the amide-amide hydrogen bonded NH band increased but the areas of amide-ester hydrogen bonded NH band decreased during hydrolysis.

Poly(styrene- co -styrene sulfonate) (PS-PSS) latexes have been coated with thin overlayer of polyaniline (PANI) to produce electrically conductive ‘core-shell’ particles (PANI/PS-PSS) in the size of range 30–50 nm in diameter. PS-PSS core particles were prepared by radical emulsion copolymerization and PANI was oxidatively polymerized using ammonium peroxydisulfate (APS) on the surface of PS-PSS latex. PANI thin overlayer was observed in transmission electron microscopy (TEM) images indicating polymerization of aniline takes place preferably on the PS-PSS surface rather than in the aqueous bulk phase. Elemental analysis revealed that the weight percent of styrene sulfonate in PS-PSS copolymer was ca. 5.4% and the conductivities of PANI/PS-PSS pellets were greatly increased with the increase of nitrogen content. Thermal gravimetric analysis (TGA) thermograms showed two main degradation stages beginning at 360 and 460°C that correspond to the decomposition of PS-PSS and PANI, respectively.

Conductivity stability at thermal environment of conductive polyaniline-complexes/polyimide (PANI-complexes/PI) blends, which were doped by camphorsulfonic acid (CSA) and dodecylbenzenesulfonic acid (DBSA), respectively, were investigated by conductivity measurements, electron spin resonance (ESR) spectra, differential and scanning thermometer (DSC). In the conversion process of PANI/Polyamic acid (PAA) to PANI/PI, the blend endeavored some kinds of alteration such as decomplexation of moisture and solvent, dissociation of dopant, crosslinking of PANI chain, and the imidization of PAA chain. PANI-DBSA/PI showed higher thermal stability of conductivity than PANI-CSA/PI, and both samples showed nearly linear decay of conductivity with increasing temperature showing greatly enhancement of conductivity stability. When they were exposed at near or over glass transition temperature, the conductivity decay became faster. The conductivity stability at base environment was also higher for PANI-DBSA/PI due to difficulty in accessing of hydroxyl ion to PANI, which were resulted from dopant. DBSA-doped blends showed increased polaron mobility and concentration at relatively high temperature, which led to extremely higher conductivity and its stability at high temperature. Copyright © 2002 John Wiley & Sons, Ltd.

The effect of solvent and dopant on the thermal transition of polyaniline (PANI) has been investigated principally by dynamic mechanical analysis (DMA). Solvent (NMP) containing film was found to exhibit three thermal transitions in tan δ curve (142, 198, and 272°C). The two lower transitions were disappeared when NMP was removed. Hence, the third peak was suggested to be real glass transition of PANI. The shape of DMA spectra was varied with thermal curing temperature, which is directly related to NMP content. Two other peaks seemed to be due to the evaporation of solvent existing as different environment (free NMP and hydrogen-bonded NMP), which was traced by TGA, FT-IR, and DMA with altering the curing temperature. It was suggested that the third peak was composed of cross-linking reaction between adjacent chains as well as glass transition of polyaniline backbone. NMP free films were prepared by two methods (repeating doping–dedoping cycle and thermal curing). In these films, only one tan δ was observed at over 250°C. When the NMP free film was doped, the DMA peak observed over 250°C was broadened and shifted toward lower temperature.

Small-angle X-ray scattering patterns of polyaniline (PANI) complexes/polyimide (PI) blends were observed in order to analyze the compatibility between two components of the blends. From the experimental results, it was concluded that the microphase separation or molecular level mixing, which was the reflection of compatibility, was dependent on the kinds of dopant (camphorsulfonic acid (CSA) and dodecylbenzene sulfonic acid (DBSA)), PANI content and the imidization state. On account of self-assembling nature of PANI–DBSA, PANI–DBSA/poly(amic acid) (PAA) shows phase-separated morphology. On the other hand, PANI–CSA/PAA blends exhibited well-mixed and high compatible morphology. Thermal curing of these blends brought about the change of blend morphology, which was in correlation with altered chain structure from PAA into PI, and was also a function of PANI content. It was supposed that conversion from PAA to PI by thermal curing processes led to enhancement of compatibility probably due to higher interaction between two components.

High molecular weight linear and branched poly(butylene adipate)s (PBAs) were prepared, and crystallization behavior and rheological properties were investigated. PBAs showed multiple melting behavior. Increasing molecular weight retarded the crystallization rate and increased the induction time for crystallization. Introducing branches to the polymer led to similar results. The Avrami exponent (n) for the linear and branched PBAs were 3.79–4.39 and 2.09–3.64, respectively. The Mark-Houwink exponent of the PBAs was 0.554. Unlike general-purpose polyesters, high molecular weight PBAs did not exhibit a Newtonian flow region. High molecular weight PBAs exhibited gel-like rheological properties, producing high elasticity. The slopes of a log-log plot of storage modulus (G′) vs. loss modulus (G″) ranged from 1.75 to 1.17, and the slope decreased with increasing molecular weight. For comparable molecular weights, the branched PBAs had higher viscosity and G′ than the linear polymers.

Polyaniline (PANI) dispersions consisting of 10–20 nm sized nanoparticles were prepared by oxidation with ammonium peroxydisulfate (APS) in sodium dodecylsulfate (SDS) micellar solutions. Coalescence and coagulation were prevented by electrostatic repulsive interaction between anionic SDS micelles. Particle morphology was dependent on the initial shape of surfactant aggregates (micelles) and the molar ratio of SDS to aniline monomer. Spherical particles were obtained at very low monomer concentration and the shape of particles began to be distorted from the spherical shape as monomer concentration increased at constant 0.2 M SDS concentration. The size of spherical particles was the same order of the micellar size or slightly larger. UV–VIS spectroscopy, compositions of PANI powder, morphology, crystalline structure, thermal stability, molecular weight and conductivity of PANI particles synthesized at various monomer and surfactant concentrations were investigated.

We prepared carboxylic acid group terminated linear polybutylene adipate (PBA) by melt polycondensation of adipic acid with 1,4-butanediol in the presence of titanium(IV) isopropoxide (TIP) as a catalyst. High molecular weight branched PBAs were synthesized through the branching reaction between the carboxylic acid group terminated PBA and branching agent such as glycerol or pentaerythritol in the presence of TIP. The weight-average molecular weights of the branched PBAs were found to be in the range of about 100,000–240,000 by gel permeation chromatography. Mechanical properties of the linear and branched PBAs were measured on an Instron tensile tester. The moduli of the branched PBAs had lower values of 320–450 MPa than those of the linear PBAs, whereas the elongations at break of the branched PBAs were in the range of 530–590%, which are much greater than the linear PBAs. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2143–2150, 2001

The shear-induced crystallization behavior of PET was investigated by measuring the time-dependent storage modulus (G′) and dynamic viscosity (η′) with a parallel-plate rheometer at different temperatures and shear rate. The morphology of shear-induced crystallized PET was measured by DSC, X-ray, and polarizing optical microscopy. When a constant shear rate was added to the molten polymer, the shear stress increased with the time as a result of the orientation of molecular chains. The induction time of crystallization is decreased with frequency. Moreover, the rate of isothermal crystallization of PET was notably decreased with increasing temperature. The shape of spherulites is changed to ellipsoid in the direction of shear. In addition, aggregation of spherulites is increased with increasing frequency. Particularly, the row nucleation morphology could be observed under polarized light for ω = 1. From the results of DSC, the melting point and enthalpy have a tendency to decrease slightly with increasing frequency. The crystallite size and perfectness decreased with frequency, which was confirmed with X-ray data. The unit length of the crystallographic unit cell of the PET increased and the (1 0 3) plane peak increased with increasing frequency. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2640–2646, 2001

Dielectric responses of polyaniline (PANI) salt films, made from two different methods, were compared to investigate the effect of a dopant and film-formation methods on the dielectric properties. One of the film-formation methods for emeraldine salt was the film-doping method, and the other, the solution-doping method. The conductivity relaxation and dielectric properties were measured by a microdielectrometer at 293 K in the frequency range of 1–100,000 Hz. Dielectric spectra were a function of the dopant in the case of the film-doping method, whereas it was a function of solvent–dopant combinations as well as the dopants in the solution-doping method. The dielectric responses of film-doped samples had similar patterns irrespective of the dopants, while those of solution-doped samples were varied, probably due to different conjugation conditions or/and the conduction mechanism. In the case of film-doped samples, dielectric loss and permittivity values were increased with decreasing dopant sizes. The dielectric relaxation times were also varied depending on the kind of dopants. The different solvent–dopant combinations led to variation of the dielectric responses in the solution-doped PANI due to an altered chain structure. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2760–2769, 2001

To obtain long branched polybutylene succinate (PBS), modified PBSs were prepared by introducing a branching agent, trimethylol propane (TMP), to the polycondensation system of succinic acid and 1,4-butanediol. Molecular parameters such as absolute molecular weight and root-mean-square (RMS) radius of the modified PBSs were measured by gel permeation chromatography (GPC) with a multiangle laser light-scattering (MALLS) detector. The RMS radius of TMP05, PBS prepared by incorporating 0.5 wt % TMP during polycondensation, was the smallest of all PBSs tested at the same molecular weight. The notable shear thinning and much reduced loss tangent for TMP05 qualitatively supported the difference in their molecular structures predicted by GPC. The analytical results indicated that introducing 0.5 wt % TMP produced PBS with chain branches long enough to produce molecular entanglements. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1388–1394, 2001

Gelatinized starches were prepared with various content of glycerol and were investigated in terms of the effect of the glycerol addition on characteristics of starch and its blends. Poly (L-lactic acid) (PLA) with various ratios of linear/star shaped PLA and starch gelatinized with various ratios of water/glycerol were melt-blended by using twin screw mixer. The blends were characterized by DSC thermal analysis, tensile test and morphological analysis. Gelatinization of starch was found to lead to destruction or diminution of hydrogen bonding in granules and a decrease of crystallinity of starch. DSC data showed that starch played a role as a nucleating agent and glycerol as plasticizer contributed to an improvement in crystallinity in PLA blends. When the content of starch increased, the size of spherulites in PLA blends was smaller and less regular. In the case of PLA/pure starch blends, the voids appeared, which were formed by the separation of starch particles from the matrix. But for PLA/gelainized starch blends, these voids were not observed. In the case of blends with linear PLA and starch gelatinized with water/glycerol ratio of 100/40, the greatest superiority of mechanical properties was shown and the toughness was improved compared with PLA/pure starch blends.