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A series of polypropylene carbonate (PPC)/ZnO nanocomposite films with different ZnO contents were prepared via a solution blending method. The morphological structures, thermal properties, oxygen permeability, water sorption, and antibacterial properties of the films were investigated as a function of ZnO concentration. While all of the composite films with less than 5 wt % ZnO exhibited good dispersion of ZnO in the PPC matrix, FTIR and SEM results revealed that solution blending did not lead to a strong interaction between PPC and unmodified ZnO. As such, poor dispersion was induced in the composite films with a high ZnO content. By incorporating inorganic ZnO filler nanoparticles, the diffusion coefficient, water uptake in equilibrium, and oxygen permeability decreased as the content of ZnO increased. The PPC/ZnO nanocomposite films also displayed a good inhibitory effect on the growth of bacteria in the antimicrobial analysis. The enhancement in the physical properties achieved by incorporating ZnO is advantageous in packaging applications, where antimicrobial and environmental-friendly properties, as well as good water and oxygen barrier characteristics are required. Furthermore, UV light below ∼ 350 nm can be efficiently absorbed by incorporating ZnO nanoparticles into a PPC matrix. ZnO nanoparticles can also improve the weatherability of a PPC film. In future research, the compatibility and dispersion of the PPC matrix polymer and the inorganic ZnO filler nanoparticles should be increased. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.

Four different structure polyimide thin films based on 1,4-phenylene diamine (PDA) and 4,4′-oxydianiline (ODA) were synthesized by using two different dianhydrides, pyromellitic dianhydride (PMDA) and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA), and their residual stress behavior and mechanical properties were investigated by using a thin film stress analyzer and nanoindentation method. The residual stress behavior and mechanical properties were correlated to the morphological structure in polyimide films. The morphological structure of polyimide thin films was characterized by X-ray diffraction patterns and refractive indices. The residual stress was in the range of −5 to 38 MPa and increased in the following order: PMDA-PDA < BPDA-PDA < PMDA-ODA < BPDA-ODA. The hardness of the polyimide films increased in the following order: PMDA-ODA < BPDA-ODA < PMDA-PDA < BPDA-PDA. The PDA-based polyimide films showed relatively lower residual stress and higher hardness than the corresponding ODA-based polyimide films. The in-plane orientation and molecularly ordered phase were enhanced with the increasing order as follows: PMDA-ODA < BPDA-ODA < BPDA-PDA ∼ PMDA-PDA. The PDA-based polyimides, having a rigid structure, showed relatively better-developed morphological structure than the corresponding ODA-based polyimides. The residual stress behavior and mechanical properties were correlated to the morphological structure in polyimide films. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Two series of semi-interpenetrating polymer network (semi-IPN) composite films, PEI/bismaleimide (UTBM) and PEI/fluorinated BMI (UTFBM) were prepared using a thermoplastic PEI and two different crosslinkable imide moieties. The effects of chemical structure and content of crosslinkable imide moieties on thermal stability, dielectric properties, and water sorption have been investigated. Glass transition temperature and weight loss temperatures increased with increase in the content of crosslinkable imide moieties, indicating the enhanced thermal stability of the semi-IPN composite films. The refractive indices of the semi-IPN composite systems increased with increasing crosslinkable imide moieties due to the higher polarizabilities of atoms. The water sorption of the semi-IPN composite films was significantly decreased by the incorporation of crosslinkable imide moieties, which are interpreted by morphological structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Poly(methyl methacrylate)-block-polyurethane-block-poly(methyl methacrylate) tri-block copolymers have been synthesized successfully through atom transfer radical polymerization of methyl methacrylate using telechelic bromo-terminated polyurethane/CuBr/N,N,N,N″,N″-pentamethyldiethylenetriamine initiating system. As the time increases, the number-average molecular weight increases linearly from 6400 to 37,000. This shows that the poly methyl methacrylate blocks were attached to polyurethane block. As the polymerization time increases, both conversion and molecular weight increased and the molecular weight increases linearly with increasing conversion. These results indicate that the formation of the tri-block copolymers was through atom transfer radical polymerization mechanism. Proton nuclear magnetic resonance spectral results of the triblock copolymers show that the molar ratio between polyurethane and poly (methyl methacrylate) blocks is in the range of 1 : 16.3 to 1 : 449.4. Differential scanning calorimetry results show Tg of the soft segment at −35°C and Tg of the hard segment at 75°C. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Semi-interpenetrating polymer network (semi-IPN) membranes based on novel sulfonated polyimide (SPI) and poly (ethylene glycol) diacrylate (PEGDA) have been prepared for the fuel cell applications. SPI was synthesized from 1,4,5,8-naphthalenetetracarboxylic dianhydride, 4,4′-diaminobiphenyl 2,2′-disulfonic acid, and 2-bis [4-(4-aminophenoxy) phenyl] hexafluoropropane. PEGDA was polymerized in the presence of SPI to synthesize semi-IPN membranes of different ionic contents. These membranes were characterized by determining, ion exchange capacity, water uptake, water stability, proton conductivity, and thermal stability. The proton conductivity of the membranes increased with increasing PEGDA content in the order of 10−1 S cm−1 at 90°C. These interpenetrating network membranes showed higher water stability than the pure acid polyimide membrane. This study shows that semi-IPN SPI membranes based on PEGDA which gives hydrophilic group and structural stability can be available candidates comparable to Nafion® 117 over 70°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

The features of norbornene (NE) cross-linked polyimide (PI) were investigated as the ratio of the norbornene monomer was varied. The coefficient of thermal expansion and modulus are important parameters of materials used in the microelectronic industry. Therefore, in this study, 5-norbornene-2, 3-dicarboxylic acid (NE) was introduced as a crosslinking agent to increase the thermal stability at elevated temperatures. 4,4′-Benzophenonetetracarboxylic dianhydride was utilized as a dianhydride and 4,4′-diaminodiphenyl ether was introduced as a diamine monomer. By changing the ratio of each monomer, we were able to control the spacing of the chain and ring opening polymerization, which resulted in improved properties. Each sample was thermally cured which led to a ring opening mechanism of the norbornene through the reverse Diels-Alder reaction. Thermal mechanical analysis was utilized to determine the coefficient of thermal expansion and dynamic mechanical analysis was used to determine the storage modulus (e′) and loss modulus (e″) of the PI film. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42607.

To synthesize new functional poly(urethane-imide) crosslinked networks, soluble polyimide from 2,2′-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 4,4′-oxydianiline, and maleic anhydride and polyurethane prepolymer from polycaprolactone diol, tolylene 2,4-diisocyanate and hydroxyl ethyl acrylate were prepared. Poly(urethane-imide) thin films were finally prepared by the reaction between maleimide end-capped soluble polyimide (PI) and acrylate end-capped polyurethane (PU). The effect of polyurethane content on dielectric constant, residual stress, morphology, thermal property, and mechanical property was studied by FTIR, prism coupler, Thin Film Stress Analyzer (TFSA), XRD, TGA, DMTA, and Nano-indentation. Dielectric constant of poly(urethane-imide) thin films (2.39–2.45) was lower than that of pure polyimide (2.46). Especially, poly(urethane-imide) thin films with 50% of PU showed lower dielectric constant than other poly(urethane-imide) thin films did. Lower residual stress and slope in cooling curve were achieved in higher PU content. Compared to typical polyurethane, poly(urethane-imide) thin films exhibited better thermal stability due to the presence of the imide groups. The glass transition temperature, modulus, and hardness decreased with increase in the flexible PU content even though elongation and thermal expansion coefficient increased. Finally, poly(urethane-imide) thin films with low residual stress and dielectric constant, which are strongly affected by the morphological structure, chain mobility, and modulus, can be suggested to apply for electronic devices by variation of PU. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 113–123, 2006

The effect of a crosslinkable imide moiety, bismaleimide (BMI), on the water sorption properties of poly(ether imide) (PEl) was gravimetrically measured and interpreted together with the chemical and morphological structures in composite films. The morphological structure of composite films was investigated by using a prism coupler and X-ray diffraction pattern. It indicated that the in-plane orientation and intermolecular packing order increased as the content of BMI in composite films increased. The water sorption behaviors showed dependence on the morphological change originating from the addition of BMI to PEI. The composite film with relatively high content of BMI exhibited a relatively high degree of in-plane orientation and a small mean intermolecular distance, which resulted in a decrease in the diffusion rate and water sorption and an increase in the activation energy in composite films. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1692–1697, 2006

We prepared poly(p-phenylene pyromellitimide) (PMDA–PDA), poly(p-phenylene 4,4′-hexafluoroisopropylidene diphthalimide), and their copolyimides with various compositions to explore the relationship between the water sorption and structure. The water sorption behaviors were gravimetrically investigated as a function of composition and temperature and interpreted with a Fickian diffusion model in films. Overall, the water sorption behaviors were strongly dependent on the changes in morphological structure, which originated from the variations in composition. When the content of the bulky hexafluoroisopropylidene group (6FDA) was increased, the water uptake decreased from 5.80 to 3.18 wt %, whereas the diffusion coefficient increased from 3.6 × 10−10 to 11.3 × 10−10 cm2/s. The relatively high water uptake in the PMDA–PDA polyimide film was successfully healed by the incorporation of 6FDA, which may have resulted from the increases in the intermolecular packing order and hydrophobicity. The degree of orientation and crystallinity, which are in-plane characteristics, were directly correlated to the diffusion coefficient and activation energy in the polyimide film. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3442–3446, 2003

In this study, 2,7-diamino-9-fluorenol (DAF) has been introduced to bond silica to the main chain of the polyimide (PI) copolymer. DAF contains a hydroxyl group that could covalently bond with silica particles. 4,4′-(Hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 4,4′-oxydianiline (4,4′-ODA) have been used as monomers to form a copolymer with DAF. The variation of silica content was controlled as 5%, 7.5, 10, 12.5 wt %. Variation in silica content contributes to the formation of various size (100–410 nm) of macroporous voids after hydrofluoric acid (HF) treatment. HF etching process was introduced to dissolve the silica and form voids in the structure of PI copolymer films. Compared with conventional PI films, air voids that were formed in the PI copolymer film reduced the dielectric from 4.40 to 1.86. The reduction in the dielectric constants can be explained in terms of creating silica particles that increase the presence of air voids after HF treatment. The thermal stability was stable up to 500 °C and the modulus change was confirmed with a dynamic mechanical analysis (DMA) to evaluate the effect of silica on thermal and mechanical properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 135, 45982.

To determine the thermal characteristics of linear and crosslinked polyimides (PIs), BTDA, ODPA, and 6FDA were used to synthesize polyimides. Thermal degradation temperature and glass transition temperature of the resulting PIs were measured using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). To measure the change in modulus and coefficient of thermal expansion (CTE) depending on dianhydride structure, a dynamic mechanical analyzer (DMA) and thermo-mechanical analyzer (TMA) were used. The thermal degradation and glass transition temperature properties of linear PIs varied according to whether the linear chain adopted a bulky or flexible structure. Dynamic modulus and thermal expansion values of linear polyimides also showed good agreement with the TGA and DSC results. As we expected, linear polyimide with bulky 6FDA groups showed better thermal behavior than the flexible polyimides. Crosslinked polyimide nadic end-capped (norbornene) with a bulky dianhydride group had a lower thermal degradation temperature and higher CTE than flexible BTDA and ODPA polyimides. Our results indicate that the mobility of the dianhydride group affects the thermal behaviors of linear and crosslinked polyimides in different ways. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41412.

This work demonstrates that extrusion process can be used as a continuous reactor for the recycling of crosslinked polyethylene (XLPE) via supercritical methanol decrosslinking reaction. The multistage single screw extruder (L/D = 36, D = 40 mm) with methanol injection pump was customized for the continuous supercritical decrosslinking reaction. Reaction temperature was ranged from 360°C to 390°C. The amount of methanol was varied from 0 to 7 mL/min. The extruder provided the crosslinked polymers with the supercritical conditions of methanol during continuous process. The gel content of XLPE decreased with the increase in the reaction temperature and methanol content. Although XLPE experienced supercritical methanol for less than 2 min retention time in the continuous supercritical extruder, it was completely decrosslinked above 390°C at the methanol feeding rate of 7 mL/min. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41442.

The water diffusion behaviors and activation energies of PDA- and ODA-based polyimide thin films were quite dependent on both the chemical structure and the morphological structure in the films. The water diffusion coefficients of polyimide thin films increased with increasing temperature. The activation energies varied in the range of 5.81 to 9.27 kcal/mol and were relatively higher for the PDA-based polyimide thin films than for the corresponding ODA-based polyimide thin films. For the PDA- and ODA-based polyimide films, the differences in the morphological structures and the chemical affinity to water molecules might be reflected directly on the water diffusion behaviors. The PDA-based polyimide films exhibited a relatively more ordered morphological structure (high crystallinity and good in-plane orientation) than that of the corresponding ODA-based polyimide thin films, which may serve as impenetrable obstacles for the water diffusion in the out-of-plane direction. Consequently, it may lead to a relatively slower water diffusion and high activation energy in the PDA-based polyimide thin films. Additionally, the PDA-based polyimide films with relatively lower chemical affinity showed relatively low diffusion coefficients and high activation energies. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 731–737, 2001

For the biphenyltetracarboxylic dianhydride (BPDA)-based polyimide thin films, the water sorption behaviors were gravimetrically investigated by using a thin film diffusion analyzer. The water sorption behaviors of the polyimide thin films are quite different and strongly dependent upon the sort of polyimide. The diffusion coefficients of the polyimide thin films vary in the range of 1.6 × 10−10 to 12.4 × 10−10cm2/s and the water uptakes vary from 1.52 to 5.25 wt %. Both the diffusion coefficient and water uptake of the polyimide thin films are in the increasing order: BPDA-pPDA < BPDA-p,p′ODA < BPDA-p,m′ODA < BPDA-mPDA ∼ BPDA-p,p′DDS < BPDA-m,m′DDS. Specifically, the polyimide films with para-oriented linkages in backbone structure showed relatively lower diffusion coefficient and water uptake than the corresponding polyimide films with meta-oriented linkages because of the well-developed crystalline structure and good intermolecular chain ordering. In addition, the polyimide thin films having higher chain order showed relatively lower diffusion coefficient and water uptake. The crystallinity and intermolecular chain ordering in the morphological structure are critical parameters in controlling the water sorption behaviors of the polyimide thin films. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2121–2127, 2001

Four different p-PDA–based polyimide thin films were prepared from their respective poly(amic acid)s through thermal imidization at 400°C: poly(p-phenylene pyromellitimide) (PMDA-PDA); poly(p-phenylene biphenyltetra carboximide) (BPDA-PDA); poly(p-phenylene 3,3′,4,4′-oxydiphthalimide) (ODPA-PDA); and poly(p-phenylene 4,4′-hexafluoroisopropylidene diphthalimide) (6FDA-PDA). Water-sorption behaviors of polyimide films were gravimetrically investigated at 25°C and 22–100% relative humidity by using the modified electromicrobalance (Thin Film Diffusion Analyzer). The diffusion coefficients of water for the polyimides varies in the range of 1.6 to 10.5 × 10−10 cm2/s, and are in the increasing order: BPDA-PDA < PMDA-PDA ∼ ODPA-PDA < 6FDA-PDA. The water uptakes of polyimides vary from 1.46 to 5.80 wt %, and are in the increasing order: BPDA-PDA < ODPA-PDA < 6FDA-PDA < PMDA-PDA. The water-sorption behaviors for the p-PDA–based polyimides are closely related to the morphological structure; specifically, the diffusion coefficients in p-PDA–based polyimide thin films are closely related to the in-plane orientation and mean intermolecular distance, whereas the water uptakes are affected by the packing order. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1315–1323, 2000

The effect of curing history on the residual stress behaviors in semiflexible structure poly(4,4′-oxydiphenylene pyromellitimide) (PMDA–ODA) and rigid structure poly(p-phenylene biphenyltetracarboximide) (BPDA–PDA) polyimide was investigated. Depending upon the curing history and different structures of polyimide, the residual stress behaviors and the morphology of polyimide thin films were detected in situ by using a wafer bending technique and wide angle X-ray diffraction (WAXD), respectively. For the rigid structure BPDA–PDA polyimide, the residual stress and the slope decreased from 11.7 MPa and 0.058 MPa/°C to 4.2 MPa and 0.007 MPa/°C as the curing temperature increased, and the annealing process is done. However, for the semiflexible structure PMDA–ODA, the change of the residual stress and the slope was relatively not significant. In addition, it was found that the cured polyimide prepared at a higher temperature with a multistep curing process showed a higher order of chain in-plain orientation and packing order than does the polyimide film prepared at a lower temperature with a one-step curing process. These residual stress behaviors of polyimide thin films show good agreement with WAXD results, such as polyimide chain order, orientation, and intermolecular packing order, due to curing history. Specifically, it shows that the effect of curing history on residual stress as well as morphological change was significant in rigid BPDA–PDA polyimide but, not in semiflexible PMDA–ODA polyimide. Therefore, it suggests that the morphological structure depends upon curing history, and the polyimide backbone structure might be one of important factors to lead the low residual stress in polyimide thin films. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3287–3298, 1999

Four different UV-curable poly(urethane acrylate)s were prepared through the reaction of two diisocyanates [i.e., toluene-2,4-diisocyanate (TDI) and isophorone diisocyanate (IPDI)] and two polyols [i.e., polycaprolactone triol (PCLT) and polycaprolactone diol (PCLD)], and they were characterized with Fourier transform infrared spectroscopy. The mechanical properties, thermal properties, and water sorption of the cured poly(urethane acrylate)s were also investigated with respect to the chemical structures of the polyols and diisocyanates. In comparison with linear PCLD–TDI and PCLD–IPDI, crosslinked PCLT–TDI and PCLT–IPDI with trifunctional PCLT showed relatively high thermal decomposition temperatures. The hardness and modulus of the UV-cured poly(urethane acrylate) films, which were measured by a nanoindentation technique, were in the following increasing order: PCLD–IPDI ∼ PCLD–TDI < PCLT–IPDI ∼ PCLT–TDI. The pencil hardness was 3H for PCLT–IPDI and PCLT–TDI and HB for PCLD–IPDI and PCLD–TDI. Two urethane acrylates prepared from the trifunctional polyol showed better acid and alkali resistances than those made from the bifunctional polyol. These mechanical properties and chemical resistances may have been strongly dependent on the chain flexibility of the molecules and crosslinking density. Regardless of the functionality in the polyol, the change in the yellowness index showed a lower value in the poly(urethane acrylate) coating containing the aliphatic diisocyanate IPDI in comparison with the corresponding poly(urethane acrylate) with the aromatic diisocyanate TDI. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

A series of photoinitiator-free photosensitive polyimides (PSPIs) with lower dielectric constants have been synthesized by reaction of fluorine aromatic diamine, 2,2′-bis(3-amino-4-hydroxyphenyl)hexafluoropropane diamine (AHHFP) with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and a mixture of various mole ratios of 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) by using solution poly-condensation reaction at room temperature and further imidization at 180°C. These aromatic polyimides were further acrylated via a reaction with acryloyl chlroride in the presence of triethyl amine to produce negative photoinitiator-free PSPIs. All the photoinitiator-free photosensitive polyimides were characterized by FTIR and NMR while their morphologhy was evaluated by X-ray diffractions study. These newly synthesized PSPIs were evaluated to determine their electrical, thermal, and photolithographic properties. The PSPI (AHHFP-BTDA-6FDA [1 : 0.5 : 0.5]) with high mole ratio of 6FDA showed lower dielectric constants of 2.420 at 1 kHz and 2.170 at 1 MHz in capacitance and optical methods, respectively. Further, the acrylated AHHFP-BTDA showed the highest photosensitivity than other PSPIs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010