Interfacial structure and properties of polyurethane/poly(methylacrylate-co-styrene) coating to regenerated cellulose film

A semiinterpenetrating polymer network (IPN) containing 72 wt % polyurethane (PU) and 6 wt % poly(methylacrylate-co-styrene) [P(MA-St)] was coated onto surfaces of regenerated cellulose (RC) film, which was prepared by coagulating a cellulose cuoxam from bagasse pulp. The interfacial structures, bonding manner, and the strength of the coated film were studied by infrared (IR),¹³C nuclear magnetic resonance (NMR), differential thermal analysis (DTA), transmission electron microscopy (TEM), and electron probe microscopy analysis (EPMA). It was shown that the RC film coated with PU/P(MA-St) has strong interfacial interactions, where covalent and hydrogen bonds are formed across the interface between cellulose and the PU/P(MA-St) coating. The interfacial structure of the coated film is regarded as a shared PU network crosslinked simultaneously with P(MA-St) and cellulose film. The tensile strength, water resistivity, and optical transmission of the coated films were considerably higher than that of the uncoated films. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 2495–2501, 1997     

Investigation of the curing kinetics of polyurethane/nitrocellulose blends through FT-IR measurements

Polyester (HTPS) based polyurethane (PU) elastomers were currently established to be effective binders for high-energy composites with improved performances. Conventional PU binders are mostly non-energetic materials, and consequently reduce the energy performance significantly. Nitrocellulose (NC), is an energetic polymer widely used as an ingredient in propellants, explosives, fireworks, and gas generators, it may be introduced in PU-based compositions to overcome their performance drawback. Kinetic parameters must be specified in order to build PU binders with the most convenient and appropriate features. Therefore, the cure kinetics of polyester based polyurethane binder systems were investigated by Fourier transform infrared spectroscopy (FT-IR) isothermal method. The polyester prepolymer (Desmophen^® 1200) was cured with hexamethylene diisocyanate (HDI: Desmodur^® N100) at various molar ratios (R_[NCO]/[OH] = 0.6, 1, 1.25, and 1.5) and under different isothermal conditions (T = 60°C, 80°C, 100°C, and 120°C). In addition, the effect of the addition of nitrocellulose on the kinetics of polymerization of PU was investigated. The progression of the reaction was followed based on the decrease of the peak intensity of –NCO group at 2271 cm⁻¹ as a function of the reaction time. The curing kinetic model and the apparent activation energy (E_α) were determined by the use of Kamal autocatalytic model and Friedman isoconversional method, respectively.     

Polyisobutylene‐based polyurethanes X: PU nanocomposites with s‐containing soft segments

Sulfur‐containing polyisobutylene (PIB)‐based polyurethane nanocomposite (PIB_s‐PU/NC) was synthesized using HO? CH₂CH₂? S? PIB? S? CH₂CH₂? OH for the soft segment, conventional hard segments of MDI and BDO, and organically modified montmorillonite (OmMMT) nanolayers. The properties of PIB_s‐PU/NC containing 72.5% PIB and 0.5% OmMMT were studied and contrasted with unmodified PIB_s‐PU. PIB_s‐PU/NC produces colorless optically clear films exhibiting enhanced tensile strength, elongation, oxidative–hydrolytic stability, and creep resistance relative to that of PIB_s‐PU. FTIR spectroscopy indicates H bonded S atoms between soft and hard segments, and OmMMT nanolayers. DSC and XRD suggest randomly dispersed low‐periodicity crystals and urea groups between galleries. We propose that minute amounts of OmMMT nanolayers become covalently attached to polyurethane chains and beneficially affect properties by acting as co‐chain extender/reinforcing filler. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2760–2765     

Polymer grafting onto polyurethane backbone via Diels–Alder reaction

The aliphatic polyurethane with pendant anthracene moieties (PU‐anthracene) was prepared from polycondensation of anthracen‐9‐yl methyl 3‐hydroxy‐2‐(hydroxymethyl)‐2‐methylpropanoate (anthracene diol), 1 with hexamethylenediisocyanate in the presence of dibutyltindilaurate in CH₂Cl₂ at room temperature for 10 days. Thereafter, the PU‐anthracene (M_n,GPC = 12,900 g/mol, M_w/M_n = 1.87, relative to PS standards) was clicked with a linear α‐furan protected‐maleimide terminated‐poly(methyl methacrylate) (PMMA‐MI) (M_n,GPC = 2500 g/mol, M_w/M_n = 1.33), or ‐poly(ethylene glycol) (PEG‐MI) (M_n,GPC = 550 g/mol, M_w/M_n = 1.09), to result in well‐defined PU‐graft copolymers, PU‐g‐PMMA (M_n,GPC = 23800 g/mol, M_w/M_n = 1.65, relative to PS standards) or PU‐g‐PEG (M_n,GPC = 11,600 g/mol, M_w/M_n = 1.45, relative to PS standards) using Diels–Alder reaction in dioxane/toluene at 105 °C. The Diels–Alder grafting efficiencies were found to be over 93–99% using UV spectroscopy. Moreover, the structural analyses and the thermal transitions of all copolymers were determined via ¹H NMR and DSC, respectively. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 521–527     

A route toward multifunctional polyurethanes using triple click reactions

The aliphatic polyurethane with pendant alkyne, perfluorophenyl, and anthracene moieties (PU‐anthracene) was prepared from polycondensation of anthracene, alkyne, and perfluorophenyl functional‐diols with hexamethylenediisocyanate in the presence of dibutyltindilaurate (DBTL) in CH₂Cl₂ at room temperature for 10 days. Thereafter, the PU‐(anthracene‐co‐alkyne‐co‐perfluorophenyl) (M_n,GPC = 15,400 g/mol, M_w/M_n= 1.37, relative to PS standards) was sequentially clicked with benzyl azide, octylamine, and 4‐(2‐hydroxyethyl)?10‐oxa‐4‐azatricyclo[5.2.1.02,6]dec‐8‐ene‐3,5‐dione (adduct alcohol) via copper‐catalyzed azide‐alkyne cycloaddition, active ester substitution and Diels–Alder reactions, respectively, to finally yield PU‐(hydroxyl‐co‐benzyltriazole‐co‐octylamine). The PUs were characterized using ¹H NMR, GPC, and DSC. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 480–486     

Polystyrene‐b‐poly(2,2,2‐trifluoroethyl acrylate)‐b‐polystyrene copolymers: Synthesis and fabrication of their hydrophobic porous films,spheres, and fibers

New block copolymers Polystyrene‐b‐poly (2,2,2‐trifluoroethyl acrylate)‐b‐Polystyrene (PS‐PTFEA‐PS) with controlled molecular weight (M_n=5000‐11000 g?mol^?1) and narrow molecular weight distribution (M_w/M_n=1.13‐1.17) were synthesized via RAFT polymerization. The molecular structure and component of PS‐PTFEA‐PS block copolymers were characterized through ¹H NMR, ¹⁹F NMR, GPC, FT‐IR and elemental analysis. The porous films of such copolymers with average pore size of 0.80‐1.34 μm and good regularity were fabricated via a static breath‐figure (BF) process. The effects of solvent, temperature, and polymer concentration on the surface morphology of such film were investigated. In addition, microstructured spheres and fibers of such block copolymers were fabricated by electrospinning process and observed by scanning electron microscopy (SEM). Furthermore, the hydrophobicity of porous films, spheres, and fibers was investigated. The porous film showed a good hydrophobicity with the water‐droplet contact angles of 129°, and the fibers showed higher hydrophobicity with the water‐droplet contact angles of 142°. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 678–685     

Polyurethane elastomers based on amphiphilic poly(caprolactone)‐b‐poly(butadiene)‐b‐poly(caprolactone) triblockcopolyols

Hydroxyl‐terminated poly(butadiene) (HTPB; M_n = 2100 g mol⁻¹) was capped with 30 and 60 wt % of ɛ‐caprolactone to reach amphiphilic triblock copolymers in form of capped poly(butadiene) CPB. The former (CPB30; M_n = 3300 g/mol) is amorphous with a glass temperature of −56 °C. CPB60 (M_n = 4000 g mol⁻¹) is semi‐crystalline with a melting point of 50 °C and a glass transition at −47 °C. The CPBs, HTPB and polycaprolactone diol (M_n = 2000 g mol⁻¹) were used as soft segment components in the preparation of polyurethane elastomers (PUE), using a 1/1 mixture of an MDI prepolymer and uretonimine modified MDI, and hard phase components in form of 1,3‐propane diol, 1,4‐butane diol, and 1,5‐pentane diol. CPB‐based elastomers with 1,4 butane diol (8 wt %) show hard domains as fringed aggregates with a better connection to the continuous phase than the HTPB‐based PUE. The soft segment glass transition temperature (T_g) is at −28 °C for HTPB‐based PUE and at −43 °C for those of CPB. The tensile strength of the CPB30&60‐based PUE is found between 20 and 30 MPa at an elongation at break of 400% and 550%, respectively. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 1162–1172     

Dynamic light scattering studies of atactic and syndiotactic poly(methyl methacrylate)s in dilute theta solution

The present article considers the coil‐to‐globule transition behavior of atactic and syndiotactic poly(methyl methacrylates), (PMMA) in their theta solvent, n‐butyl chloride (nBuCl). Changes in Rh in these polymers with temperature in dilute theta solutions were investigated by dynamic light scattering. The hydrodynamic size of atactic PMMA (a‐PMMA‐1) in nBuCl (M_w: 2.55 × 10⁶ g/mol) decreases to 61% of that in the unperturbed state at 13.0°C. Atactic PMMA (a‐PMMA‐2) with higher molecular weight (M_w: 3.3 × 10⁶ g/mol) shows higher contraction in the same theta solvent (α_η = R_h(T)/R_h (θ) = 0.44) at a lower temperature, 7.25°C. Although syndiotactic PMMA (s‐PMMA) has lower molecular weight than that of atactic samples (M_w: 1.2 × 10⁶), a comparable chain collapse was observed (α_η = 0.63) at 9.0°C. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2253–2260, 1999     

The effect of light on the viscosity and molecular mass of nitrocellulose

The photodegradation of a series of nitrocellulose (NC) samples with nitrogen contents ranging from 11.69% to 13.55% has been investigated by observing changes in molecular mass and viscosity using, respectively, size exclusion chromatography (SEC) and a modified cone and plate rheometer. When NC in γ-butyrolactone was subjected to UV light in the range 320-390 nm its specific viscosity (η_sp) was found to decrease noticeably, a change attributed to polymer chain scission and de-aggregation. This view was supported by an observed reduction in the mass average molecular mass (M_w). In contrast, irradiation with a single wavelength at 365 nm did not significantly change either η_sp or M_w and similar behaviour was observed when NC solutions were irradiated with visible light (400-500 nm). In the solid state, the photodegradation of water-wet NC is faster than that of the dried material, which is attributed to the catalytic effect of acids formed from the reaction between water and nitrogen oxides (NO_x) arising from NC decomposition. A higher degree of crystallinity in the NC, as found by X-ray diffraction (XRD), was shown to lead to a smaller decrease in viscosity and molecular mass. This is thought to be because the photodegradation reaction is suppressed in crystalline NC by more effective radical-radical recombination.     

Synthesis of poly(ethylene‐co‐vinyl alcohol)‐g‐polystyrene graft copolymer and their applications for ordered porous film and compatibilizer

A series of new functional poly(ethylene‐co‐vinyl alcohol)‐g‐polystyrene graft copolymers (EVAL‐g‐PS) with controlled molecular weight (M_n = 38,000–94,000 g mol^?1) and molecular weight distribution (M_w/M_n = 2.31–3.49) were synthesized via a grafting from methodology. The molecular structure and component of EVAL‐g‐PS graft copolymers were confirmed by the analysis of their ¹H NMR spectra and GPC curves. The porous films of such copolymers were fabricated via a static breath‐figure (BF) process. The influencing factors on the morphology of such porous films, such as solvent, temperature, polymer concentration, and molecular weight of polymer were investigated. Ordered porous film and better regularity was fabricated through a static BF process using EVAL‐g‐PS solution in CHCl₃. Scanning electron microscopy observation reveals that the EVAL‐g‐PS graft copolymer is an efficient compatibilizer for the blend system of low‐density polyethylene/polystyrene. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 516–524     

Analysis of polystyrene surface properties on thin film bonding under carbon dioxide pressure using nanoparticle embedding technique

A gold nanoparticle embedding technique is used to determine how vacuum and pressured carbon dioxide (CO₂) affect polystyrene (PS) thin film properties. The pressured CO₂ greatly increased the gold nanoparticle embedding depth, possibly due to a low cohesive energy density near the film surface. For the monodisperse PS used in this study (M_n = 214,000), two spin‐coated thin films with intimate contact can be bonded below the bulk glass transition temperature (T_g) under CO₂ pressure when the embedded depth is larger than half of the gyration radius of PS molecules. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1535–1542, 2009     

Unexpected Molecular Weight Dependence to the Physical Aging of Thin Polystyrene Films Present at Ultra‐High Molecular Weights

The physical aging behavior, time‐dependent densification, of thin polystyrene (PS) films supported on silicon are investigated using ellipsometry for a large range of molecular weights (MWs) from M_w = 97 to 10,100 kg mol^?1. We report an unexpected MW dependence to the physical aging rate of h < 80‐nm thick films not present in bulk films, where samples made from ultra‐high MWs ≥ 6500 kg mol^?1 exhibit on average a 45% faster aging response at an aging temperature of 40 °C compared with equivalent films made from (merely) high MWs ≤ 3500 kg mol^?1. This MW‐dependent difference in physical aging response indicates that the breadth of the gradient in dynamics originating from the free surface in these thin films is diminished for films of ultra‐high MW PS. In contrast, measures of the film‐average glass transition temperature T _g(h) and effective average film density (molecular packing) show no corresponding change for the same range of film thicknesses, suggesting physical aging may be more sensitive to differences in dynamical gradients. These results contribute to growing literature reports signaling that chain connectivity and entropy play a subtle, but important role in how glassy dynamics are propagated from interfaces. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1224–1238     

Interpenetrating polymer networks of polyurethane and graft vinyl ester resin–polyurethane formed with diphenylmethane diisocyanate

For enhancing the compatibility and/or the interpenetration of the simultaneous interpenetrating networks (SINs) composed of polyurethane (PU) formed with uretonimine modified 4,4′‐diphenylmethane diisocyanate and vinyl ester resin (VER), a series of graft VERs consisting of different lengths of side chains were synthesized and characterized. It was found that there exists some limited short‐range order due to the strong hydrogen bonding in the graft VER network composed of butanol side chains (BO‐g‐VER). The graft VER network composed of poly(oxypropylene) (PPO) side chains (M_n: 200, 200‐g‐VER) showed compatible system, while the VER network consisting of longer PPO grafts (M_n: 390, 390‐g‐VER) exhibited microphase separated morphology. Based upon the DSC and FTIR measurements as well as the SEM and TEM observation, the lengths of side chains existing in graft VER network have great effect on the morphologies of PU/graft VER SINs. For PU/BO‐g‐VER SINs, there has been some interpenetration between the two networks because of the miscibility between the BO‐g‐VER network and the hard segments existing in the PU network. For PU/200‐g‐VER SINs, the good compatibility and/or the interpenetration between the two phases was observed, since the long‐range ordered structure of hard segments in PU phase was greatly suppressed, resulting from the excellent miscibility between the urethane groups as well as the PPO side chains existing in the 200‐g‐VER network and those in the PU network, respectively. Thus, the strong reinforcement effect of these two graft networks on the PU network and the excellent mechanical properties of the SIN systems were observed. However, the PU/390‐g‐VER SINs showed the complicated morphologies because of existing microphase‐ separated morphology of 390‐g‐VER network in itself. In this case, the enhancement effect of such a graft VER network on the PU network is limited. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 136–144, 2000     

Scalings of fluorine‐containing polyimides in cyclopentanone

Eight 2,2′‐bis(3,4‐dicarboxyphenyl) hexafluoropropane dianhydride‐4,4′‐diamino‐3,3′‐dimethylbiphenyl (6FDA‐OTOL) fractions and seven 2,2′‐bis[4‐(3,4‐dicarboxyphenoxy) phenyl] propane dianhydride‐4,4′‐diamino‐3,3′‐dimethylbiphenyl (BISADA‐OTOL) fractions in cyclopentanone at 30 °C were characterized by a combination of viscometry and static and dynamic laser light scattering (LLS). In static LLS, the angular dependence of the absolute scattered intensity led to the weight‐average molar mass (M_w), the z‐average root mean square radius of gyration, and the second virial coefficient. In dynamic LLS, the Laplace inversion of each measured intensity–intensity time correlation function resulted in a corresponding translational diffusion coefficient distribution [G(D)]. The scalings of 〈D〉 (cm²/s) = 8.13 × 10⁻⁵ M_w^−0.47 and [η] (dL/g) = 2.36 × 10⁻³ M_w^0.54 for 6FDA‐OTOL and 〈D〉 (cm²/s) = 3.02 × 10⁻⁴ M_w^−0.60 and [η] (dL/g) = 2.32 × 10⁻³ M_w^0.53 for BISADA‐OTOL were established. With these scalings, we successfully converted each G(D) value into a corresponding molar mass distribution. At 30 °C, cyclopentanone is a good solvent for BISADA‐OTOL but a poor solvent for 6FDA‐OTOL; this can be attributed to an ether linkage in BISADA‐OTOL. Therefore, BISADA‐OTOL has a more extended chain conformation than 6FDA‐OTOL in cyclopentanone. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2077–2080, 2000     

Thermochemistry of the binary system nitrocellulose+2,4-dinitrotoluene

Melting enthalpy and mixing enthalpy of binary system 2,4-dinitrotoluene and nitrocellulose were determined by DSC method. The maximum value of mixing enthalpy was H _max ^M=1.38 kJ mol⁻¹ for molar fraction x _w24DNT = 0.501. The Flory-Huggins parameter (c) was estimated. The solubility curves and glass transition temperatures were predicted and compared with the experimental results. The measurements were performed for the samples with different times of storage at room temperature. The analysis of melting peaks for the mixture leads to the conclusion that for the long periods of storage the melting of 2,4-dinitrotoluene takes place in the confined spaces (pores) and unconfined space (bulk). The crystallization and melting is observed during the short time of storage in mixtures with low nitrocellulose content and in the case of mixtures with a large amount of NC the glass transition is additionally observed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis of poly(p‐phenylene) macromonomers and multiblock copolymers

Rigid‐rod poly(4′‐methyl‐2,5‐benzophenone) macromonomers were synthesized by Ni(0) catalytic coupling of 2,5‐dichloro‐4′‐methylbenzophenone and end‐capping agent 4‐chloro‐4′‐fluorobenzophenone. The macromonomers produced were labile to nucleophilic aromatic substitution. The molecular weight of poly(4′‐methyl‐2,5‐benzophenone) was controlled by varying the amount of the end‐capping agent in the reaction mixture. Glass‐transition temperatures of the macromonomers increased with increasing molecular weight and ranged from 117 to 213 °C. Substitution of the macromonomer end groups was determined to be nearly quantitative by ¹H NMR and gel permeation chromatography. The polymerization of a poly(4′‐methyl‐2,5‐benzophenone) macromonomer [number‐average molecular weight (M_n) = 1.90 × 10³ g/mol; polydispersity (M_w)/M_n = 2.04] with hydroxy end‐capped bisphenol A polyaryletherketone (M_n = 4.50 × 10³ g/mol; M_w/M_n = 1.92) afforded an alternating multiblock copolymer (M_n = 1.95 × 10⁴ g/mol; M_w/M_n = 6.02) that formed flexible, transparent films that could be creased without cracking. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3505–3512, 2001     

Novel silver‐loaded semi‐interpenetrating polymer network gel films with antibacterial activity

Novel semi‐interpenetrating polymer networks (SIPNs) based on segmented polyurethane‐urea and poly(N‐isopropylacrylamide‐co‐acrylic acid‐co‐butylmethacrylate) (poly(NIPAM‐co‐AA‐BMA)) were synthesized for the fabrication of silver nanoparticles (AgNPs) in the SIPN system that could be useful for wound dressing applications. The obtained SIPN films, after neutralization, showed high swelling in aqueous environments and good mechanical properties in both dry and hydrated states. Analysis of the dried SIPN films by differential scanning calorimetry and dynamic viscoelastic measurements revealed the presence of crosslinked copolymers as well as homopolymers in the SIPN system. The neutralized swollen SIPN film coordinated with the silver ions (Ag⁺) that were incorporated into it. AgNPs were subsequently formed by the reduction of Ag⁺. The formation of AgNPs was characterized by UV‐visible spectroscopy, atomic force microscopy, wide‐angle X‐ray diffraction, and thermogravimetric analysis (TGA). Bactericidal activity tests revealed a distinct zone of microbial inhibition within and around the silver‐doped SIPN films. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4950–4962, 2009     

Preparation of high‐temperature polyurethane by alloying with reactive polyamide

A series of novel poly(urethane amide) films were prepared by the reaction of a polyurethane (PU) prepolymer and a soluble polyamide (PA) containing aliphatic hydroxyl groups in the backbone. The PU prepolymer was prepared by the reaction of polyester polyol and 2,4‐tolylenediisocyanate and then was end‐capped with phenol. Soluble PA was prepared by the reaction of 1‐(m‐aminophenyl)‐2‐(p‐aminophenyl)ethanol and terephthaloyl chloride. The PU prepolymer and PA were blended, and the clear, transparent solutions were cast on glass substrates; this was followed by thermal treatments at various temperatures to produce reactions between the isocyanate group of the PU prepolymer and the hydroxyl group of PA. The opaque poly(urethane amide) films showed various properties, from those of plastics to those of elastomers, depending on the ratio of the PU and PA components. Dynamic mechanical analysis showed two glass‐transition temperatures (T_g's), a lower T_g due to the PU component and a higher T_g due to the PA component, suggesting that the two polymer components were phase‐separated. The rubbery plateau region of the storage modulus for the elastic films was maintained up to about 250 °C, which is considerably higher than for conventional PUs. Tensile measurements of the elastic films of 90/10 PU/PA showed that the elongation was as high as 347%. This indicated that the alloying of PU with PA containing aliphatic hydroxyl groups in the backbone improved the high‐temperature properties of PU and, therefore, enhanced the use temperature of PU. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3497–3503, 2002     

Properties of nitrocellulose‐coated and polyethylene‐laminated chitosan and whey films

Chitosan (chitosan acetic acid salt) and whey (65% protein) films were coated with a nitrocellulose lacquer or laminated with polyethylene to enhance their water resistance and gas barrier properties in humid environments. The barrier properties were measured by the Cobb₆₀ test and water‐vapor (100% relative humidity) transmission and oxygen (90% relative humidity) permeability tests. Mechanical properties were obtained with tensile tests. Packaging properties were studied with crease and folding tests. The Cobb₆₀ test revealed that the coated films were resistant to liquid water, at least for a short exposure time, if the coating thickness was at least 10–17 μm. Water‐vapor transmission rates comparable to those of polyethylene‐laminated films were obtained for coated chitosan at a coating thickness of 5–7 μm. The coated films possessed low oxygen permeability despite the high humidity. Coated films dried for 3 weeks showed oxygen permeabilities at 90% relative humidity that were similar to values for dry ethylene‐co‐vinyl alcohol at 0% relative humidity. The lacquer partly penetrated the whey films, and this led to excellent adhesion but poor lacquer toughness. The lacquer coating on chitosan was tougher, and it was possible to fold these films 90° without the coating fracturing if the coating thickness was small. The coated whey films were readily creasable. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 985–992, 2001     

Synthesis and characterization of poly(urethane‐benzoxazine) films as novel type of polyurethane/phenolic resin composites

Poly(urethane‐benzoxazine) films as novel polyurethane ( PU )/phenolic resin composites were prepared by blending a benzoxazine monomer ( Ba ) and PU prepolymer that was synthesized from 2,4‐tolylene diisocyanate (TDI) and polyethylene adipate polyol (MW ca. 1000) in 2 : 1 molar ratio. DSC of PU/Ba blend showed an exotherm with maximum at ca. 246 °C due to the ring‐opening polymerization of Ba, giving phenolic OH functionalities that react with isocyanate groups in the PU prepolymer. The poly(urethane‐benzoxazine) films obtained by thermal cure were transparent, with color ranging from yellow to pale wine with increase of Ba content. All the films have only one glass transition temperature (T_g ) from viscoelastic measurements, indicating no phase separation in poly(urethane‐benzoxazine) due to in situ polymerization. The T_g increased with the increase of Ba content. The films containing 10 and 15% of Ba have characteristics of an elastomer, with elongation at break at 244 and 182%, respectively. These elastic films exhibit good resilience with excellent reinstating behavior. The films containing more than 20% of Ba have characteristics of plastics. The poly(urethane‐benzoxazine) films showed excellent resistance to the solvents such as tetrahydrofuran, N,N‐dimethyl formamide, and N‐methyl‐2‐pyrrolidinone that easily dissolve PU s. Thermal stability of PU was greatly enhanced even with the incorporation of a small amount of Ba . © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 4165–4176, 2000