Melt‐processable blends of ionic poly(p‐phenylene terephthalamide) and poly(4‐vinylpyridine): Relaxation behavior

Melt‐processable blends were prepared from rigid molecules of an ionically modified poly(p‐phenylene terephthalamide) (PPTA) and flexible‐coil molecules of poly(4‐vinylpyridine) (PVP). Dynamic mechanical analyses of blends with 50% or more of the ionic PPTA component revealed the presence of two distinct phases. The glass‐transition temperature of the more stable, ionic PPTA‐rich phase increased linearly with the ionic PPTA content. The second phase present in these blends was an ionic PPTA‐poor, or a PVP‐rich, phase. For this phase, a reasonably good fit of the data, showing the glass‐transition temperature as a function of the ionic PPTA content, was achieved between the results of this study and the reported results of previous investigation of molecular composites of the same two components with ionic PPTA contents of 15 wt % or less. The possible influence of annealing on the blend structure of a 90/10 blend of ionic PPTA and PVP was examined. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1468–1475, 2003     

Mechanical properties of molecular composites. I. Poly (p‐phenylene terephthalamide) anion molecules dispersed in poly(4‐vinylpyridine)

Molecular composites have been prepared by dispersing rigid‐rod molecules of ionically‐modified poly(p‐phenylene terephthalamide) (PPTA anion) in a polar poly(4‐vinylpyridine) (PVP) matrix. For concentrations up to 5 wt % of the rigid‐rod reinforcement, the resulting composites are transparent and possess a single glass transition temperature that increases with concentration of the PPTA anion. The mechanical properties of the molecular composites are found to increase with concentration and to attain maximum values at about 5 wt % of the PPTA anion. The enhancement in properties, and the miscibility induced between the two component polymers, is attributed to the development of specific interactions between the ionic groups of the PPTA anion and the polar units of the PVP matrix. When such interactions are not present, as in composites reinforced with non‐ionic PPTA, the samples are opaque and their properties are significantly reduced compared to those of the PPTA anion/PVP composites. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2201–2209, 1999     

Molecular composites made of ionic poly(p‐phenylene terephthalamide) and poly(4‐vinylpyridine): Relaxation behavior

Molecular composites were prepared from several types of ionically modified, poly(p‐phenylene terephthalamide) (PPTA) dispersed in a poly(4‐vinylpyridine) matrix. Optical clarity tests indicated that the component polymers of the composite were miscible, at least at low concentrations of the rodlike reinforcement. In composites containing ionic PPTA, where ionic sulfonate groups were attached as side groups either to PPTA chains or to PPTA anion chains, the glass‐transition temperature (T_g) was increased by l0 °C or more, at 5 wt % reinforcement. At concentrations of 10–15 wt % of the ionic polymer, T_g values leveled off or decreased slightly. This suggested that some aggregation of the rigid‐rod molecules occurred. In composites containing ionic PPTA, where the ionic sulfonate groups were directly attached to the phenylene rings of PPTA chains, not only was T_g shifted significantly to higher temperatures, but the rubbery plateau modulus retained high values up to temperatures of 250 °C or above. Observed effects were considered to be the result of strong ionic interactions between the ionic reinforcement polymer and the polar matrix polymer. The possible effects of the counterion on T_g and the storage modulus are discussed. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1110–1117, 2002     

Linear and four‐armed poly(l‐lactide)‐block‐poly(d‐lactide) copolymers and their stereocomplexation with poly(lactide)s

Linear and four‐armed poly(l ‐lactide)‐block‐poly(d ‐lactide) (PLLA‐b‐PDLA) block copolymers are synthesized by ring‐opening polymerization of d ‐lactide on the end hydroxyl of linear and four‐armed PLLA prepolymers. DSC results indicate that the melting temperature and melting enthalpies of poly (lactide) stereocomplex in the copolymers are obviously lower than corresponding linear and four‐armed PLLA/PDLA blends. Compared with the four‐armed PLLA‐b‐PDLA copolymer, the similar linear PLLA‐b‐PDLA shows higher melting temperature (212.3 °C) and larger melting enthalpy (70.6 J g^?1). After these copolymers blend with additional neat PLAs, DSC, and WAXD results show that the stereocomplex formation between free PLA molecular chain and enantiomeric PLA block is the major stereocomplex formation. In the linear copolymer/linear PLA blends, the stereocomplex crystallites (sc) as well as homochiral crystallites (hc) form in the copolymer/PLA cast films. However, in the four‐armed copolymer/linear PLA blends, both sc and hc develop in the four‐armed PLLA‐b‐PDLA/PDLA specimen, which means that the stereocomplexation mainly forms between free PDLA molecule and the inside PLLA block, and the outside PDLA block could form some microcrystallites. Although the melting enthalpies of stereocomplexes in the blends are smaller than that of neat copolymers, only two‐thirds of the molecular chains participate in the stereocomplex formation, and the crystallization efficiency strengthens. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 1560–1567     

Thermal and mechanical properties of mandelic acid‐copolymerized poly(butylene succinate) and poly(ethylene adipate)

Phenyl side chains were introduced to poly(butylene succinate) and poly(ethylene adipate) by the polymerization of the respective monomers in the presence of mandelic acid. The increasing content of the phenyl side chains decreased the melting temperature and the crystallinity but increased the glass‐transition temperature of the aliphatic polyesters. The phenyl side branches reduced the crystallinity of poly(butylene succinate) more significantly than the ethyl or n‐octyl side branches did. The tensile strength, elongation, and tear strength of poly(ethylene adipate) decreased with an increase in the content of mandelic acid units. However, the increasing content of mandelic acid units enhanced the elongation and tear strength of poly(butylene succinate) considerably without a notable deterioration of tensile strength. The biodegradability of the copolyesters was increased as a result of the introduction of more mandelic acid units due to the decrease in the crystallinity. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1504–1511, 2000     

Miscibility,crystallization kinetics,and morphology of poly(β‐hydroxybutyrate) and poly(methyl acrylate) blends

The miscibility, spherulite growth kinetics, and morphology of binary blends of poly(β‐hydroxybutyrate) (PHB) and poly(methyl acrylate) (PMA) were studied with differential scanning calorimetry, optical microscopy, and small‐angle X‐ray scattering (SAXS). As the PMA content increases in the blends, the glass‐transition temperature and cold‐crystallization temperature increase, but the melting point decreases. The interaction parameter between PHB and PMA, obtained from an analysis of the equilibrium‐melting‐point depression, is −0.074. The presence of an amorphous PMA component results in a reduction in the rate of spherulite growth of PHB. The radial growth rates of spherulites were analyzed with the Lauritzen–Hoffman model. The spherulites of PHB were volume‐filled, indicating the inclusion of PMA within the spherulites. The long period obtained from SAXS increases with increased PMA content, implying that the amorphous PMA is entrapped in the interlamellar region of PHB during the crystallization process of PHB. All the results presented show that PHB and PMA are miscible in the melt. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1860–1867, 2000     

Origin of double melting behavior of poly(p‐phenylene succinate)

The origin of double melting behavior of poly(p‐phenylene succinate) (PPSc) was investigated by differential scanning calorimetry (DSC) and wide‐angle X‐ray diffraction. As‐polymerized PPSc showed two melting peaks: the low melting (LM) and high melting (HM) peaks at 286 and 311 °C, respectively. When PPSc was annealed at 270 °C, the LM peak constantly shifted toward higher temperatures and grew in its area with annealing time, and eventually merged into the HM peak located at 308 °C. X‐ray diffractograms of PPSc annealed at 270 °C became sharper with increasing the annealing time while the peak positions did not change. The X‐ray diffractograms obtained from the LM and the HM peak exhibited the same diffraction peaks. It was concluded from these results that the double melting behavior of PPSc is due to the distribution of crystals having the same crystal form but differing in size and perfection. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1868–1871, 2000     

Isothermal melt and cold crystallization kinetics of poly(aryl ether ketone ether ketone ketone)

The isothermal melt and cold crystallization kinetics of poly(aryl ether ketone ether ketone ketone) are investigated by differential scanning calorimetry over two temperature regions. The Avrami equation describes the primary stage of isothermal crystallization kinetics with the exponent n ≈ 2 for both melt and cold crystallization. With the Hoffman–Weeks method, the equilibrium melting point is estimated to be 406 °C. From the spherulitic growth equation proposed by Hoffman and Lauritzen, the nucleation parameter (K_g) of the isothermal melt and cold crystallization is estimated. In addition, the K_g value of the isothermal melt crystallization is compared to those of the other poly(aryl ether ketone)s. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1992–1997, 2000     

Miscibility,melting, and crystallization of poly(butylene‐2,6‐naphthalate)/poly(ether imide) blends

We prepared blends of poly(butylene‐2,6‐naphthalate) (PBN) and poly(ether imide) (PEI) by solution‐casting from dichloroacetic acid solutions. The miscibility, crystallization, and melting behavior of the blends were investigated with differential scanning calorimetry (DSC) and dynamic mechanical analysis. PBN was miscible with PEI over the entire range of compositions, as shown by the existence of single composition‐dependent glass‐transition temperatures. In addition, a negative polymer–polymer interaction parameter was calculated, with the Nishi–Wang equation, based on the melting depression of PBN. In nonisothermal crystallization investigations, the depression of the crystallization temperature of PBN depended on the composition of the blend and the cooling rate; the presence of PEI reduced the number of PBN segments migrating to the crystallite/melt interface. Melting, recrystallization, and remelting processes occurring during the DSC heating scan caused the occurrence of multiple melting endotherms for PBN. We explored the effects of various experimental conditions on the melting behavior of PBN/PEI blends. The extent of recrystallization of the PBN component during DSC heating scans decreased as the PEI content, the heating rate, the crystallization temperature, and the crystallization time increased. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1694–1704, 2004     

High‐pressure DTA of poly(butylene terephthalate), poly(hexamethylene terephthalate), and poly(ethylene terephthalate)

Pressure effect on the melting behavior of poly(butylene terephthalate) (PBT) and poly(hexamethylene terephthalate) (PHT) was studied by high‐pressure DTA (HP‐DTA) up to 320 and 530 MPa, respectively. Cooling rate dependence on the DSC melting curves of the samples cooled from the melt was shown at atmospheric pressure. Stable and metastable samples were prepared by cooling from the melt at low and normal cooling rates, respectively. DTA melting curves for the stable samples showed a single peak, and the peak profile did not change up to high pressure. Phase diagrams for PBT and PHT were newly determined. Fitting curves of melting temperature (T_m) versus pressure expressed by quadratic equation were obtained. Pressure coefficients of T_m at atmospheric pressure, dT_m/dp, of PBT and PHT were 37 and 33 K/100 MPa, respectively. HP‐DTA curves of the metastable PBT showed double melting peaks up to about 70 MPa. In contrast, PHT showed them over the whole pressure region. HP‐DTA of stable poly(ethylene terephthalate) (PET) was also carried out up to 200 MPa, and the phase diagram for PET was determined. dT_m/dp for PET was 49 K/100 MPa. dT_m/dp increased linearly with reciprocal number of ethylene unit. The decrease of dT_m/dp for poly(alkylene terephthalate) with increasing a segmental fraction of an alkyl group in a whole molecule is explained by the increase of entropy of fusion. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 262–272, 2000     

Miscibility and spherulite growth kinetics in the poly(ethylene oxide)/poly(benzyl methacrylate) system

This study for the first time discovered miscibility in the binary blend of semicrystalline poly(ethylene oxide) (PEO) with amorphous poly(benzyl methacrylate) (PBzMA). Differential scanning calorimetry, optical and scanning electron microscopy, and infrared spectroscopy were performed to characterize and demonstrate miscibility in the PEO/PBzMA system. The glass‐transition behavior and Fourier transform infrared results suggest that the intermolecular interactions between the pairs were likely nonspecific and at best comparable to those among the same constituent component. The melting‐point depression study yielded χ = −0.1, indicating a relatively low interaction strength. It is concluded that the phase behavior of the blend was miscibility with nonspecific interactions, mostly a matched polar–polar intermolecular attraction. PEO spherulitic crystallization in the blend is discussed to support the miscibility behavior. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 562–572, 2000     

New insight into melting and crystallization behavior in semicrystalline poly(ethylene terephthalate)

After isothermal crystallization, poly(ethylene terephthalate) (PET) showed double endothermic behavior in the differential scanning calorimetry (DSC) heating scan. During the heating scans of semicrystalline PET, a metastable melt which comes from melting thinner lamellar crystal populations formed between the low and the upper endothermic temperatures. The metastable melt can recrystallize immediately just above the low melting temperature and form thicker lamellae than the original ones. The thickness and perfection depends on the crystallization time and crystallization temperature. The crystallization kinetics of this metastable melt can be determined by means of DSC. The kinetics analysis showed that the isothermal crystallization of the metastable PET melt proceeds with an Avrami exponent of n = 1.0 ∼ 1.2, probably reflecting one‐dimensional or irregular line growth of the crystal occurring between the existing main lamellae with heterogeneous nucleation. This is in agreement with the hypothesis that the melting peaks are associated with two distinct crystal populations with different thicknesses. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 53–60, 2000     

Preparation and characterization of biodegradable poly(trimethylenecarbonate‐ε‐caprolactone)‐block‐poly(p‐dioxanone) copolymers

A series of poly(trimethylenecarbonate‐ε‐caprolactone)‐block‐poly(p‐dioxanone) copolymers were prepared with varying feed rations by using two step polymerization reactions. Poly(trimethylenecarbonate)(ε‐caprolactone) random copolymer was synthesized with stannous‐2‐ethylhexanoate and followed by adding p‐dioxanone monomer as the other block. The ring opening polymerization was carried out at high temperature and long reaction time to get high molecular weight polymers. The monofilament fibers were obtained using conventional melting spun methods. The copolymers were identified by ¹H and ¹³C NMR spectroscopy and gel permeation chromatography (GPC). The physicochemical properties, such as viscosity, molecular weight, melting point, glass transition temperature, and crystallinity, were studied. The hydrolytic degradation of copolymers was studied in a phosphate buffer solution, pH = 7.2, 37 °C, and a biological absorbable test was performed in rats. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2790–2799, 2005     

The degree of crystallinity of monoclinic isotactic poly(propylene)

The degree of crystallinity of a set of monoclinic (alpha) isotactic poly(propylenes), prepared by a metallocene‐type catalyst, were determined at room temperature. Three different methods were used: density, enthalpy of fusion, and wide‐angle X‐ray scattering, and the results compared. The relation between the heat of fusion and the specific volume of these poly(propylenes) was found to be nonlinear, thus precluding any linear extrapolation to obtain the heat of fusion of the pure crystal (ΔH_u). The value of ΔH_u obtained from depression of the melting temperature by diluents is used. Based on the unit cell density of monoclinic crystals formed from a low defected fraction, the density obtained crystallinity levels were found to be between 0.l5–0.25 higher than those calculated from the heat of fusion. This relatively large difference holds for the isothermally crystallized and quenched isotactic poly(propylenes), and reflects the contribution of the interphase to the density determined crystallinity, which does not contribute to the heat of fusion. Paralleling results found in other systems, the crystallinity levels obtained from wide‐angle X‐ray scattering agree with those obtained from density, indicating a significant contribution of the partially ordered phase to the total diffraction. Emphasis is given on the need to account for the large differences in the crystallinities of poly(propylene) measured by different techniques when evaluating the dependence of properties on this quantity. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 323–334, 1999     

Heat capacity and thermodynamic functions of crystalline poly(p‐phenylenebenzobisoxazole), the synthetic polymer with the highest Young's modulus

The heat capacity of crystalline poly(p‐phenylenebenzobisoxazole) was measured below room temperature by adiabatic calorimetry. The standard thermodynamic functions (enthalpy, entropy, and Gibbs energy) were established and tabulated. The temperature dependence of the heat capacity was compared with those of polyethylene and poly(p‐phenylene), with attention paid to the low dimensionality of the systems. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1584–1588, 2000     

Morphology of poly(butylene terephthalate)–poly(ethylene terephthalate‐co‐isophthalate‐co‐sebacate) segmented copolyesters

Segmented copolyesters, namely, poly(butylene terephthalate)–poly(ethylene terephthalate‐co‐isophthalate‐co‐sebacate) (PBT‐PETIS), were synthesized with the melting transesterification processing in vacuo condition involving bulk polyester produced on a large scale (PBT) and ternary amorphous random copolyester (PETIS). Investigations on the morphology of segmented copolyesters were undertaken. The two‐phase morphology model was confirmed by transmission electron microscopy and dynamic mechanical thermal analysis. One of the phases was composed of crystallizable PBT, and the other was a homogeneous mixture of PETIS and noncrystallizable PBT. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2257–2263, 2003     

Complexation of linear and poly(ethylene oxide)‐grafted poly(methacryl oxyethyl trimethylammonium chloride) with poly(ethylene oxide‐block‐sodium methacrylate)

The interactions between oppositely charged polyelectrolytes were studied in saline aqueous solutions as functions of the temperature and the salt and polymer concentrations. The polyanion was a diblock copolymer composed of a poly(ethylene oxide) block and a poly(sodium methacrylate) block. Two polycations were used, the homopolymer poly(methacryl oxyethyl trimethylammonium chloride) and its poly(ethylene oxide)‐grafted analogue. By dynamic light scattering and turbidity measurements, it was observed that the salt concentration, temperature, and counterion size had a significant effect on the formation of the polymer complexes in aqueous solutions. At a fixed salt concentration and a fixed temperature, it was possible to form completely soluble complexes of an ionic polymer in aqueous solutions between poly(ethylene oxide)‐grafted poly(methacryl oxyethyl trimethylammonium chloride)and the polyanion with a poly(ethylene oxide) block at a 1:1 anion/cation ratio. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1904–1914, 2003     

Poly(ester anhydride)s prepared by the insertion of ricinoleic acid into poly(sebacic acid)

New degradable poly(ester anhydride)s were prepared by the melt polycondensation of diacid oligomers of poly(sebacic acid) (PSA) transesterified with ricinoleic acid. The transesterification of PSA with ricinoleic acid to form oligomers was conducted via a melt bulk reaction between a high molecular weight PSA and ricinoleic acid. A systematic study on the synthesis, characterization, degradation in vitro, drug release, and stability of these polymers was performed. Polymers with weight‐average molecular weights of 2000–60,000 and melting temperatures of 24–77 °C were obtained for PSA containing 20–90% (w/w) ricinoleic acid. NMR and IR analyses indicated the formation of ester bonds along the polyanhydride backbone. These new degradable copolymers have potential use as drug carriers. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1059–1069, 2003     

Side‐chain crystallization behavior of graft copolymers consisting of an amorphous main chain and crystalline side chains. II. Poly(n‐hexyl methacrylate)‐graft‐poly(ethylene glycol)

The phase behavior and crystallization of graft copolymers consisting of poly(n‐hexyl methacrylate) (PHMA) as an amorphous main chain and poly(ethylene glycol) (PEG) as crystallizable side chains (HMAx with 15 ≤ x ≤ 73, where x represents the weight percentage of PEG) were investigated. Small‐angle X‐ray scattering profiles measured above the melting temperature of PEG suggested that a microdomain structure with segregated PHMA and PEG domains was formed in HMA40 and HMA46. This phase behavior was qualitatively described by a calculated phase diagram based on the mean‐field theory. Because of the segregation of PEG into microdomains, the crystallization temperature of the PEG side chains in HMAx was higher than that in poly(methyl acrylate)‐graft‐poly(ethylene glycol) having a similar value of x, which was considered to be in a disordered state above the melting temperature. In HMAx with x ≤ 40, PEG crystallization was strongly restricted, probably because the PEG microdomains were isolated in the PHMA matrix. As a result, the growth of PEG spherulite was not observed because the PEG crystallization occurred after vitrification of the PHMA segregated domains. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 129–137, 2007     

Synthesis and properties of novel poly(arylene ether)s and poly(arylene thioether)s based on a pyridazine biphenol or a phthalazine biphenol

Novel sulfur‐containing biphenol monomers were prepared in high yields by the reaction of 4‐mercaptophenol with chloropyridazine or chlorophthalazine compounds. High‐molecular‐weight poly(arylene ether)s were synthesized by a nucleophilic substitution reaction between these sulfur‐containing monomers and activated difluoro aromatic compounds. The inherent viscosities of these polymers ranged from 0.34 to 0.93 dL/g. The poly(pyridazine)s exhibited glass‐transition temperatures greater than 165 °C. The poly(phthalazine)s showed higher glass‐transition temperatures than the poly(pyridazine)s. A polymer synthesized from a bisphthalazinebiphenol and bis(4‐fluorophenyl)sulfone had the highest glass‐transition temperature (240 °C). The thermal stabilities of the poly(pyridazine)s and poly(phthalazine)s showed similar patterns of decomposition, with no significant weight loss below 390 °C. The poly(phthalazine)s were soluble in chlorinated solvents such as chloroform, and the poly(pyridazine)s were soluble in dipolar aprotic solvents such as N,N′‐dimethylacetamide. The soluble poly(pyridazine)s and poly(phthalazine)s could be cast into flexible films from solution. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 262–268, 2007