Electrical functionalities of poly(n‐hexyl isocyanate) in solid phase

We report electrical functionalities of a rigid rod‐like helical polymer, poly(n‐hexyl isocyanate) (PHIC), in the solid state. Our experimental results of a displacement (D)–field (E) hysteresis and a measurement of pyroelectric signal proved that the PHIC system was electrically active. From the D–E hysteresis loop, coercive field and remanent polarization were determined to be 6.8 MV/m and 3.0 mC/m², respectively, at 80 °C. The pyroelectric coefficient was 9.5 mC/m² K for the sample for which the poling treatment was conducted at 80 °C with the field 20 MV/m. The dipole ordering of the C?O dipoles attached to the main chain was responsible for these electrical activities. Relatively small amounts of the remanent polarization and the pyroelectric coefficient possibly resulted from the short‐range dipole ordering in the noncrystalline phase. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3093–3099, 2005     

Solution properties of poly(dimethyl siloxane)

The solution properties of poly(dimethyl siloxane) (PDMS) were studied with light scattering (LS), gel permeation chromatography/light scattering (GPC/LS), and viscometry methods. PDMS samples were fractionated, and the weight‐average molecular weights, second virial coefficient, and the z‐average radius of gyration of each fraction were found according to the Zimm method with the LS technique. In this work, the molecular weight range studied was 7.5 × 10⁴ to 8.0 × 10⁵. Molecular weights and molecular weight distributions were determined by GPC/LS. The intrinsic viscosities of these fractions were studied in toluene at 30 °C, in methyl ethyl ketone (MEK) at 20 °C, and in bromocyclohexane (BCH) at 26 °C and 28 °C. The Mark–Houwink–Sakurada relationship showed that toluene was a good solvent, and MEK at 20 °C and BCH at 28 °C were θ solvents for PDMS. The unperturbed dimensions were calculated with LS and intrinsic viscosity data. The unperturbed dimensions, expressed in terms of the characteristic ratio, were found to be 6.66 with different extrapolation methods in toluene at 30 °C. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2678–2686, 2000     

Poly(phenyl methacrylate) and poly(1‐naphthyl methacrylate) prepared in microemulsions

Phenyl methacrylate and 1‐naphthyl methacrylate were polymerized in microemulsions using stearyltrimethylammonium chloride, cetyltrimethylammonium bromide, and a mixture of nonionic Triton surfactants to form latexes that were 20–30 nm in diameter. A temperature of 70 °C was needed to obtain polymers using thermal initiation. The tacticities of poly(phenyl methacrylate) (PPhMA) (55% rr) and poly(1‐naphthyl methacrylate) (P‐1‐NM) (47% rr) were the same as those of the polymers prepared in toluene solutions. The weight average molecular weights were 1 × 10⁶ and 5 × 10⁵ g/mol for PPhMA and P‐1‐NM prepared in microemulsions with very broad distributions. PPhMA samples from microemulsions and solution had the same T_g = 127 °C. P‐1‐NM from microemulsions had T_g = 145–147 °C compared with T_g = 142 °C for P‐1‐NM from solution. The molecular weights and the glass‐transition temperatures of both PPhMA and P‐1‐NM from microemulsions are substantially higher than any previously reported. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 519–524, 2001     

Synthesis and gas transport properties of high molecular weight block copolymers of styrene and vinyltrimethylsilane

Poly(styrene-b-vinyltrimethylsilane) of high molecular weight and varying composition suitable for membrane applications has been synthesized at 50–60°C. The copolymer could be made as a tapered block copolymer by polymerizing both monomers at the same time (r₁ and r₂ = 0.08 and 13) or as a pure block copolymer with some homopolymer contaminant by sequential addition of monomers. However, in both methods the copolymer phases out of solution before the reaction is complete. The copolymers can exhibit phase separation in the solid and dissolved states. Poly(styrene-b-vinyltrimethylsilane) membranes have some unique gas transport properties. The poly(vinyltrimethylsilane) segments are phase separated and dispersed in a continuous polystyrene matrix so the resultant membranes can have over twice the permeability of polystyrene but also retain the high selectivity of polystyrene. These results should be applicable to other biphasic systems where the low permeability phase is also the continuous phase. © 1993 John Wiley & Sons, Inc.     

Polymerization and polymer properties of (p-tert-butyl-o,o-dimethylphenyl)acetylene

(p-tert-Butyl-o,o-dimethylphenyl)acetylene (BDMPA) polymerized in high yields in the presence of W and Mo catalysts. Especially the W(CO)₆–CCl₄–hv catalyst quantitatively produced a polymer totally soluble in toluene and chloroform. The weight-average molecular weight of this polymer exceeded 2 × 10⁶. Poly(BDMPA) was a dark brown solid, and had alternating double bonds along the main chain. The weight loss of the polymer in air occurred only above 300°C, indicating a fairly high thermal stability. A free-standing film could be fabricated by solution casting. The electrical conductivity of the polymer at 25°C was 1 × 10⁻¹³ S cm⁻¹. The oxygen permeability coefficient and the separation factor of O₂ vs. N₂ of the polymer at 25°C were 67 barrers and 3.2, respectively. © 1996 John Wiley & Sons, Inc.     

Polymer diffusion in latex films at ambient temperature

Polymer diffusion across interfaces at room temperature (21°C) was analyzed by direct nonradiative energy transfer (DET) in labeled latex films. Two modellatex polymers were examined: poly(butyl methacrylate) [PBMA, M_w = 3.5 × 10⁴, T_g (dry) = 21°C] and a copolymer of 2-ethylhexyl methacrylate with 10 wt % (acetoacetoxy)-ethyl methacrylate [P(EHMA-co-AAEM), M_w = 4.8 × 10⁴, T_g (dry) = −7°C]. Little energy transfer due to polymer diffusion was detected for the P(EHMA-co-AAEM) latex samples in the dispersed state or dried to solids content below ca. 90%, but above 90% solids, diffusion occurs among particles. For PBMA, diffusion occurs only after the film is dried (>97% solids) and aged. In the dry PBMA films, it requires 4–5 days at 21°C to reach a significant extent of mixing (f_m = 0.3–0.4). This corresponds to an estimated penetration depth d_app of 30–40 nm and a mean apparent diffusion coefficient (D_app) of 5 × 10⁻⁴ nm²/s. The corresponding D_app value for the dry P(EHMA-co-AAEM) sample is 5 × 10⁻² nm²/s, and it takes about 25–40 min for this polymer to reach f_m of 0.3–0.4 with d_app of 20–30 nm. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 1129–1139, 1998     

Syntheses and self‐assembly of poly(benzyl ether)‐b‐poly(N‐isopropylacrylamide) dendritic–linear diblock copolymers

This article describes the syntheses and solution behavior of model amphiphilic dendritic–linear diblock copolymers that self‐assemble in aqueous solutions into micelles with thermoresponsive shells. The investigated materials are constructed of poly(benzyl ether) monodendrons of the second generation ([G‐2]) or third generation ([G‐3]) and linear poly(N‐isopropylacrylamide) (PNIPAM). [G‐2]‐PNIPAM and [G‐3]‐PNIPAM dendritic–linear diblock copolymers have been prepared by reversible addition–fragmentation transfer (RAFT) polymerizations of N‐isopropylacrylamide with a [G‐2]‐ or [G‐3]‐based RAFT agent, respectively. The critical micelle concentration (cmc) of [G‐3]‐PNIPAM₂₂₀, determined by surface tensiometry, is 6.3 × 10^?6 g/mL, whereas [G‐2]‐PNIPAM₂₃₅ has a cmc of 1.0 × 10^?5 g/mL. Transmission electron microscopy results indicate the presence of spherical micelles in aqueous solutions. The thermoresponsive conformational changes of PNIPAM chains located at the shell of the dendritic–linear diblock copolymer micelles have been thoroughly investigated with a combination of dynamic and static laser light scattering and excimer fluorescence. The thermoresponsive collapse of the PNIPAM shell is a two‐stage process; the first one occurs gradually in the temperature range of 20–29 °C, which is much lower than the lower critical solution temperature of linear PNIPAM homopolymer, followed by the second process, in which the main collapse of PNIPAM chains takes place in the narrow temperature range of 29–31 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1357–1371, 2006     

Stress-optical properties of poly(oxypropylene) networks

Strain birefringence of poly(oxypropylene) was studied using several poly(oxypropylene) model networks of different crosslink densities. Most of the measurements were carried out in elongation, in both the unswollen and the swollen states, over the temperature range 10–70°C. The optical configuration parameter was found to be Δa = (4.33 ± 0.09) × 10^?24 cm³ at 25°C with a very small temperature coefficient. Theoretical calculations based on rotational isomeric state theory were employed to interpret the experimental data. The results indicate the intermolecular correlations to be low for this polymer, and, contrary to other systems, the stress-optical coefficient C decreased with increasing average molecular weight between crosslinks. This fact was attributed to the end-group effect introduced by the crosslinking agent.     

Thermoelastic and dielectric studies of poly(3,3-dimethyl oxetane) chains

Poly(3,3-dimethyl oxetane) was synthesized by ring opening polymerization of 3,3-dimethyl oxetane. Elongation experiments were performed on unswollen elastomeric networks prepared from this polymer over the temperature range 30–90°C. The changes in the tensile stress while the networks crystallized were examined at various elongations. From thermoelastic data which were free from the effects of network crystallization, the temperature coefficient of the chain dimensions was found to be 1.1 × 10^?3 K^?1 in the vicinity of 60°C. The dipole moment ratio and its temperature coefficient were also measured; the average values of these parameters at 30°C were 0.20₆ and 2.5 × 10^?3 K^?1, respectively. All of these experimental-configuration-dependent properties were critically interpreted in terms of the rotational isomeric-state model. In comparing theory and experiment, conclusions were obtained which confirm earlier results according to which gauche states about C—C skeletal bonds in poly(3,3-dimethyl oxetane) are strongly favored over the alternative trans states.     

Kinetics of metal exchange reaction of Cu(II)-poly(vinyl alcohol) complex with Ca(II)-ethylenediamine-N,N,N′,N′-tetraacetic acid in aqueous solution

The kinetics of the metal exchange reaction between the Cu(II)-poly(vinyl alcohol) complex (Cu(II)-PVA) and Ca(II)-ethylenediamine-N,N,N′,N′-tetraacetic acid (Ca(II)-EDTA) were studied by mixing both solutions in a spectrophotometer at pH 9.7–11.0, at μ = 0.10(KNO₃) and at 25°C. The reaction is initiated by the formation of unstable Cu(II)-H-PVA by the attack of H⁺ to Cu(II)-PVA, and while both ligand exchange and metal exchange steps occur, the latter may be rate-determining. The kinetic expression of this reaction was determined as -d[Cu(II)-PVA]/dt = k[Cu(II)-PVA] [H⁺] [PVA]/[Ca(II)-EDTA], where k = k₁ + k′₂[H⁺], k₁ = 3.85 × 10⁻² sec⁻¹, k₂ = k′₂ · K^−H_Cu(II)-H-PVA 9.59 × 10⁵ 1 mol⁻¹ sec⁻¹.     

New poly(amide-imide)s syntheses. VIII. Preparation and properties of poly (amide-imide)s derived from 2,3-bis(4-aminophenoxy)naphthalene,trimellitic anhydride,and various aromatic diamines

The new polymer-forming diimide-diacid, 2,3-bis(4-trimellitimidophenoxy) naphthalene (I), was readily obtained by the condensation reaction of 2,3-bis (4-aminophenoxy) naphthalene with trimellitic anhydride. A series of novel aromatic poly (amide-imide)s were prepared by the direct polycondensation of diimide-diacid I with various aromatic diamines using triphenyl phosphite in N-methyl-2-pyrrolidone (NMP)/pyridine solution containing dissolved calcium chloride. The resultant polymers have inherent viscosities in the range of 0.65–1.02 dL/g at 30°C in N, N-dimethylacetamide. These polymers were readily soluble in various organic solvents and could be cast into transparent, tough, and flexible films. Their casting films showed tensile strength at break up to 86 MPa, elongation to break of 5–9%, and initial moduli up to 2.35 GPa. The wide-angle X-ray diffraction revealed that those polymers containing p-phenylene or p-oxyphenylene group are partially crystalline, and the other polymers are evidenced as amorphous patterns. These polymers show a glass transition in the range of 213–290°C in their differential scanning calorimetry (DSC) traces. The thermal stability of the polymers was evaluated by thermogravimetry analysis, which showed the 10% weight-loss temperatures in the range of 508–565°C in nitrogen and 480–529°C in air atmosphere. © 1994 John Wiley & Sons, Inc.     

Synthesis,pH‐ and temperature‐induced micellization and gelation of doubly hydrophilic triblock copolymer of poly(N,N‐dimethylamino‐2‐ethylmethacrylate)‐b‐poly(ethylene glycol)‐b‐poly(N,N‐dimethylamino‐2‐ethylmethacrylate) in aqueous solutions

A doubly hydrophilic triblock copolymer of poly(N,N‐dimethylamino‐2‐ethyl methacrylate)‐b‐Poly(ethylene glycol)‐b‐poly(N,N‐dimethylamino‐2‐ethylmethacrylate) (PDMAEMA‐b‐PEG‐b‐PDMAEMA) with well‐defined structure and narrow molecular weight distribution (M_w/M_n = 1.21) was synthesized in aqueous medium via atom transfer radical polymerization (ATRP) of N,N‐dimethylamino‐2‐ethylmethacrylate (DMAEMA) initiated by the PEG macroinitiator. The macroinitiator and triblock copolymer were characterized with ¹H NMR and gel permeation chromatography (GPC). Fluorescence spectroscopy, dynamic light scattering (DSL), transmittance measurement, and rheological characterization were applied to investigate pH‐ and temperature‐induced micellization in the dilute solution of 1 mg/mL when pH > 13 and gelation in the concentrated solution of 25 wt % at pH = 14 and temperatures beyond 80 °C. The unimer of R_h = 3.7 ± 0.8 nm coexisted with micelle of R_h = 45.6 ± 6.5 nm at pH 14. Phase separation occurred in dilute aqueous solution of the triblock copolymer of 1 mg/mL at about 50 °C. Large aggregates with R_h = 300–450 nm were formed after phase separation, which became even larger as R_h = 750–1000 nm with increasing temperature. The gelation temperature determined by rheology measurement was about 80 °C at pH 14 for the 25 wt % aqueous solution of the triblock copolymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5869–5878, 2008     

NLO‐active maleimide copolymers with ­high glass transition temperatures

We synthesized some novel rigid NLO‐active maleimide copolymers bearing DR‐1 moieties ( PMPD , PHSD and PHND ). All copolymers exhibited high T_g's (190～197 °C), good solubilities for common solvents and excellent film‐forming properties. Dependence of film thickness on the d₃₃ value for the poled copolymer films induced by corona poling was investigated and it was demonstrated that in less than thickness of 0.3 µm decrease of the thickness gives rise to remarkable increase in the d₃₃ value. The poled copolymer films exhibited large d₃₃ values (270 × 10^?9 esu (film thickness 0.13 µm) for PMPD , 290 × 10^?9 esu (0.12 µm) for PHSD and 350 × 10^?9 esu (0.08 µm) for PHND ) as well as large r₃₃ values (51.0 pmV^?1 for PMPD and 60.4 pmV^?1 for PHND ) which are significantly large compared to the value of LiNbO₃ (31 pmV^?1) as a typical EO material. The d₃₃ values of the poled copolymers were kept constant even after standing 1000h at 80 °C, although a small decrease was observed at an initial stage. Further, the d₃₃ values did not change up to ca. 123 °C upon heating at the rate of 10 °C/min in all cases. Copyright © 2002 John Wiley & Sons, Ltd.     

Viscoelastic behaviors and molecular motions of highly syndiotactic poly(vinyl alcohol) fibers

The viscoelastic behavior and molecular motion of highly syndiotactic poly(vinyl alcohol) (S‐PVA) fibers with a dyad syndiotacticity (r) of 69% were studied by dynamic mechanical thermal analysis and wide‐angle X‐ray diffraction and compared with those of atactic poly(vinyl alcohol) (A‐PVA) fibers with r = 54%. The β_c dispersion, based on the molecular motion of the chain molecules in the crystalline regions, was observed for A‐PVA around 120–140 °C, and the only primary (α_c) dispersion was observed for S‐PVA around 180 °C. The thermal expansion coefficients for the a and c axes of the A‐PVA crystal changed discontinuously around 120 °C, which corresponded to the β_c dispersion. For S‐PVA, the coefficient for the (002) plane changed discontinuously around 100 °C, similarly to A‐PVA, but that for the (100) plane remained unchanged between 20 and 220 °C. These results showed that the intermolecular hydrogen bonding of S‐PVA was stronger in the direction of the a axis than in the other directions, suppressing the β_c dispersion. The storage modulus and thermal expansion coefficient of the (020) plane (molecular axis) of S‐PVA decreased markedly around 180 °C, and this indicated that the α_c dispersion was due to the torsional motion of the molecular chains in the crystalline regions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 800–808, 2004     

Synthesis and properties of a poly(diphenylacetylene) containing carbazolyl groups

1-(p-N-Carbazolylphenyl)-2-phenylacetylene (p-CzDPA) was polymerized by TaCl₅–co-catalyst systems (cocatalysts: n-Bu₁Sn, Et₃SiH, and 9BBN) to produce acetone-insoluble polymers in about 60-70% yields. Poly(p-CzDPA) was a yellowish-orange solid, most part of which was soluble in toluene, chloroform, etc., and its weight-average molecular weights were around 4×10⁵. This polymer formed a tough film by solution casting, and was thermally very stable (the onset temperature of weight loss in TGA in air 470°C). The oxygen per-meability coefficient of the polymer at 25°C was lower than two barrers. The present polymer showed photoconductivity and redox activity. © 1995 John Wiley & Sons, Inc.     

Small‐angle X‐ray scattering study of a weak polyelectrolyte in water

Small‐angle X‐ray scattering (SAXS) was used to obtain solution parameters of a weak polyelectrolyte in water in the absence of any additives, such as neutralizing agents or salt. Poly(acrylic acid) (PAA) was used as a weak polyelectrolyte from which SAXS data were obtained in the dilute region of 1–10 mg cm^?3. An intrinsic viscosity of 15.7 dL g^?1 was obtained from a plot of reciprocal reduced viscosities versus the concentration. The application of the SAXS data, that is, the contour length (L = 1.97 × 10⁴ Å), the persistence length (a* = 58.5 Å), and the molecular weight (M = 5.9 × 10⁵ Da), to the Yamakawa–Fujii equation suggested that PAA in water at 25 °C could be described as a wormlike chain having a cylindrical body of d = 6 Å. An end‐to‐end distance (r = 1.6 × 10³ Å) was calculated from r = 2a*L ? 2(a*)². The nonisotropic expansion factor (α = 2.9) was calculated for PAA expanding from the random coil in dioxane at 30 °C (Θ temperature) to the wormlike chain in water at 25 °C. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1263–1272, 2003     

Synthesis and Characterization of Thermo-responsive Poly(N-vinyl-2-pyrrolidinone)-block-poly(N-isopropylacrylamide) Micelles

A novel thermo-responsive diblock copolymer of poly(N-vinyl-2-pyrrolidinone)-block-poly(N-isopropylacrylamide) (PNVP-b-PNIPAM) was synthesized. FT-IR, ¹H-NMR and SEC results confirmed the successful synthesis of PNVP-b-PNIPAM diblock copolymer via anionic polymerization. The polymeric micelles formed from PNVP-b-PNIPAM copolymer in aqueous solution were developed and characterized as a potential thermo-responsive and biocompatible drug delivery system. Micellization of the diblock copolymer in aqueous solution was characterized by dynamic laser scattering (DLS), turbidity measurement, tension measurement and transmission electron microscopy (TEM). The thermo-responsive polymeric micelles with the size ranges of 200 to 260 nm and thickness of 30 nm are localized, selected and targeted for drug release, having a great potential in response to external-stimulus such as temperatures from 35 to 39°C. The critical micellization concentration (cmc) of PNVP-b-PNIPAM in aqueous solution is 0.0026 wt% determined by turbidity measurement. The size of micelles determined by DLS increased from 163 to 329 nm with increasing concentration of PNVP-b-PNIPAM from 0.25 to 0.5 wt% in aqueous solution at 40°C, which is determined by DLS.     

Synthesis,Characterization, and Conductivities of Poly(2-Vinylpyridine)-graft-Polyoxyethylene Using a Macromer Technique

Abstract

Poly(2-vinylpyridine) (P2-VP) with uniform polyoxyethylene (PEO) grafts was synthesized using a macromer technique. 2-Vinylpyridine was copolymerized with PEO macromer in solution by using azobisisobutyronitrile (AIBN) as the initiator. The effects of the amount of AIBN, the concentrations of 2-vinylpyridine and macromer, the number average molecular weight of macromer, and the charging ratio of macromer to 2-vinylpyridine in the copolymerization were studied. The copolymerization rate of the PEO macromer with 2-vinylpyridine was also investigated. The grafting efficiency reached about 56%. The crude graft copolymer was purified by extraction and precipitation, and it was characterized by IR, ¹H-NMR, and Bruss membrane osmometry. The PEO grafts were doped with LiClO₄ and showed ionic conductivity around 4.10 × 10^?6S°Cm^?1 at 25°C whereas the P2-VP main chains were complexed with TCNQ to obtain electronic conductivity around 5.50 × 10^?6 S°Cm^?1 at 25°C The mixed (ionic and electronic) conductivity of the doped copolymer could reach about 5.40 × 10^?5 S°Cm^?1 at 25°C and showed a synergistic effect.     

Effect of temperature and water as additive on the MW and thermal properties of copoly(p-phenylene/biphenylene sulfide)s

Copoly(p-phenylene/biphenylene sulfide)s, PPBS were prepared from sodium sulfide trihydate(Na₂S·3H₂O), p-dichlorobenzene (DCB), and 4,4′-dibromobiphenyl (DBB) comonomers in N-methyl-2-pyrrolidinone (NMP) solvent using an autoclave. The molecular weights of PPBS copolymers were determined by high temperature (210°C) GPC in 1-chloronaphthalene solvent. The reaction temperature had little effect on the molecular weights of PPBS copolymers with water as additive at the level of 3 mol H₂O per 1 mol Na₂S. PPBS copolymer, however, showed maximum molecular weight of M_w = 24.1 × 10³ with the total water content of 9 mol H₂O per 1 mol Na₂S at an optimum polymerization temperature of 270°C. The resulting PPBS copolymer sample showed higher T_g (by 30°C) and lower T_m (by 10°C) than PPS homopolymer prepared under similar conditions. © 1996 John Wiley & Sons, Inc.     

Thermo and pH Dual-Responsive Micelles of N-phthaloylchitosan-g-Poly(N-isopropylacrylamide) and Poly(acrylic acid-co-tert-butyl acrylate) for Drug Delivery

A novel amphiphilic copolymer N-phthaloylchitosan graft poly(N-isopropylacrylamide) and poly(acrylic acid-co-tert-butyl acrylate) (PHCS-g-PNIPAAm&P(AA-co-tBA)) was synthesized. The graft copolymer could form micelles in aqueous medium, and the critical micelle concentration (CMC) of the copolymer was 7.5 × 10^{? 3}mg/mL. The lower critical solution temperature (LCST) of the micelles was measured to be 30°C. Transmission electron microscopy (TEM) image showed that the micelles exhibited a regular spherical shape, and the mean diameter of the micelles was 94.1 ± 0.8 nm as determined by dynamic light scattering (DLS). The potential usefulness of the micelles as drug delivery systems was investigated using anti-inflammation drug prednisone acetate as the model. The drug loading capacity of the micelles was measured to be 22.86 wt%, and the DLS results showed that the mean diameter of the drug-loaded micelles was 133.3 ± 2.4 nm. In vitro drug release studies indicated that the micelles exhibited thermo and pH dual-responsive release profiles.