Synthesis and thermal analysis of emulsion terpolymers of N‐phenylmaleimide,methyl methacrylate,and acrylonitrile

Terpolymers of N‐phenylmaleimide (PMI), methyl methacrylate (MMA), and acrylonitrile (AN) were synthesized by emulsion polymerization. The thermal properties of the terpolymers, at different PMI and AN feed contents, were investigated by TBA, TGA, and the Vicat softening point test. The results show that the glass transition temperature (T_g) and decomposition temperature of the terpolymers increase with increasing PMI feed content. Furthermore, the Vicat softening points of the terpolymers increase with the PMI feed content. The M?_w and M?_n of the terpolymers were also determined by GPC. The results show that the M?_w and M?_n of the terpolymers have a maximum value in the range of 0–30% PMI feed content and decrease with an increasing AN feed content. The mechanical properties (tensile strength and impact strength) of the terpolymers decrease with an increasing PMI feed content and increase with an increasing AN feed content. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2455–2462, 2001     

Synthesis and thermoanalysis of emulsion terpolymers of N‐phenylmaleimide,styrene, and acrylonitrile

Terpolymers of N‐phenylmaleimide (PMI), styrene, and acrylonitrile (AN) were synthesized by emulsion polymerization. The thermal properties of terpolymers at different PMI and AN feed contents were investigated by differential scanning calorimetry, torsional braid analysis, thermogravimetric analysis, and a Vicat softening point test. The results showed the glass‐transition temperature and decomposition temperature of the terpolymers increased with increasing PMI feed content. Furthermore, the Vicat softening point of the terpolymers rose with PMI feed content. The weight‐ and number‐average molecular weights (M̄_w and M̄_n) of the terpolymers were also determined by gel permeation chromatography. The results showed that the M̄_w and M̄_n of the terpolymers decreased with increasing PMI feed content and increased with increasing AN feed content. The mechanical properties (tensile strength and impact strength) of the terpolymers decreased with increasing PMI feed content and increased with increasing AN feed content. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1067–1073, 2001     

Preparation and identification of a soluble copolymer from pyrrole and o-toluidine

A series of copolymers were prepared by chemically oxidative polymerization of pyrrole (PY) and ortho-toluidine (OT) in HCl aqueous medium. The yield, intrinsic viscosity, and solubility of the copolymers were studied by changing the monomer molar ratio. The resulting PY/OT copolymers were identified by FTIR, ¹H–NMR, DSC, and WAXD techniques. The experimental results showed that the oxidative polymerization of pyrrole and o-toluidine is exothermic and the resulting polymers exhibit an enhanced solubility in most organic solvents compared with that of pyrrole homopolymer. The polymer obtained is a real and amorphous copolymer containing pyrrole and o-toluidine units. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 510–518, 2001     

Synthesis and characterization of suspension terpolymer of N‐cyclohexylmaleimide,methyl methacrylate,and styrene

N‐cyclohexylmaleimide (ChMI) and styrene (St) were polymerized with methyl methacrylate (MMA) at different St feed content by suspension polymerization method. The glass transition temperatures (T_g) of the terpolymers were detected by torsional braid analysis (TBA). Two transition peaks in TBA curves of the terpolymers with a high St content illustrated that these terpolymers have a heterogeneous chain structure and the phase separation occurred. The lower transition temperature, T_g1, was assigned to the random St‐MMA components, and the higher transition temperature, T_g2, was assigned to the St‐ChMI units‐rich segments. Thermogravimetric analyses (TGA) revealed that all the terpolymers showed a two‐step degradation process. The tensile strength of the terpolymers decrease with increasing St content while the impact strength tended to increase slightly. The rheological behavior of the terpolymers was also detected. The result illustrated that the terpolymers showed rheological behavior similar to that of pseudoplastic liquid. The apparent shear viscosity decreased with the increasing of St content. All terpolymers have a higher value of flow n than the poly(MMA‐co‐ChMI). © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 918–922, 2006     

The terpolymer of neodymium‐catalyzed styrene,isoprene, and butadiene: Efficient synthesis of integral rubber containing atactic styrene–styrene sequences and high Cis‐1,4 polyconjugated olefins

The present study focuses on the terpolymer of styrene (St), isoprene (Ip), and butadiene (Bd) synthesized together in cyclohexane at 70°C with neodymium (Nd) compound, alkylaluminum, and chlorinating agent (Cl) rare earth cocatalyst system. The resultants possessed atactic St–St sequences and high cis‐1,4 polyconjugated olefins in macromolecular chains besides controllable composition. The composition of the St–Ip–Bd terpolymers and molecular weight (M_w), molecular weight distribution (M_w/M_n) were controlled through the adjustment of Nd compound, alkylalumium, monomers feed ratio (St/Ip/Bd), and [Nd]/[monomers]. With the inventory rating of St raised from 15% to 55%, the content of St in the terpolymers got increased from 2% to 15%. And the content of the Ip segments and Bd segments in the terpolymers increased from 33% to 56% and from 28% to 54%, respectively, with the proportion of Ip/Bd varied from 1/2 to 2/1. As the [Nd]/[monomers] varied from 1.0 × 10^?3 to 5.0 × 10^?4, the molecular weight increased from 1.3 × 10⁴ to 2.7 × 10⁴. According to the proton nuclear magnetic resonance (¹H‐NMR) and ¹³C‐NMR, it was proved that both microstructures of polybutadiene segments and polyisoprene segments were high cis‐1,4‐configuration. A single glass‐transition temperature was observed in the differential scanning calorimetry curve. POLYM. ENG. SCI., 54:1858–1863, 2014. © 2013 Society of Plastics Engineers     

pH‐responsive polyzwitterions: A comparative study of acrylamide‐based polyampholyte terpolymers and polybetaine copolymers

A comparative study of pH‐responsive polyzwitterions (PZs) with polyampholyte or polybetaine architectures was conducted with well‐defined model polymer systems. Low‐charge‐density PZs, including ampholytic terpolymers composed of acrylamide (AM), sodium 3‐acrylamido‐3‐methylbutanoate, and (3‐acrylamidopropyl)trimethylammonium chloride and carboxybetaine copolymers composed of AM and 3‐(3‐acrylamidopropyldimethylammonio)propionate, were prepared via free‐radical polymerization in 0.5M NaCl to yield ter‐ and copolymers with random termonomer and comonomer distributions. Sodium formate was used as a chain‐transfer agent during the polymerizations to eliminate the effects of the monomer feed composition on the degree of polymerization (DP) and to suppress gel effects and broadening of the molecular weight distributions. The polymer compositions were determined via ¹³C‐NMR spectroscopy, and the residual counterion content was determined via elemental analysis for Na⁺ and Cl^?. The molecular weights (MWs) and polydispersity indices (PDIs) were determined via size exclusion chromatography/multi‐angle laser light scattering (SEC–MALLS); the polymer MWs ranged from 1.4 to 1.5 × 10⁶ g/mol, corresponding to DPs of 1.6–1.9 × 10⁴ repeat units, with all the polymers exhibiting PDIs less than or equal to 2.1. The intrinsic viscosities determined from SEC–MALLS data and the Flory–Fox relationship agreed with the intrinsic viscosities determined via low‐shear dilute‐solution viscometry. Data from the SEC–MALLS analysis were used to analyze the radius of gyration/molecular weight (R_g–M) relationships and the Mark–Houwink–Sakurada intrinsic viscosity/molecular weight ([η]–M) relationships for the PZs. The R_g–M and [η]–M relationships and viscometric data revealed that under size exclusion chromatography conditions, the poly[acrylamide‐co‐3‐(3‐acrylamidopropyldimethylammonio)propionate] betaine copolymers had more open, random‐coil conformations and greater polymer–solvent interactions than the ampholytic poly[acrylamide‐co‐sodium 3‐acrylamido‐3‐methylbutanoate‐co‐(3‐acrylamidopropyl)trimethylammonium chloride] terpolymers. The pH‐ and salt‐responsive dilute‐solution viscosity behavior of the PZs was examined to assess the effects of the polymer structure and composition on the solution properties. The polyampholyte terpolymers had greater solution viscosities and more pronounced stimuli‐responsiveness than the polybetaine copolymers because of their stronger intramolecular interactions and increased chain stiffness. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 24–39, 2004     

Synthesis and characterization of a novel oligosiloxane containing alternative ladderlike structure via charge‐transfer interaction

A novel oligosiloxane containing alternative ladderlike structure involving viologen groups has been prepared via donor–acceptor interaction‐assisted template polymerization. The monomer used as the electron‐donor component, N,N ′‐bis(3‐methyldimethoxyl‐silylpropyl)‐4,4′‐bipyridinium dihexafluorophosphate and its precursor, N,N ′‐bis(3‐methyldimethoxyl‐silylpropyl)‐4,4′‐bipyridinium dibromide were first synthesized successfully in high yield. This oligosiloxane, which displays interesting electrochromic properties, has been characterized by FTIR, UV–vis, ¹H NMR, ²⁹Si NMR, X‐ray diffraction (XRD), and vapour pressure osmometry (VPO). © 2001 Society of Chemical Industry     

Synthesis and characterization of terpolymer of N‐cyclohexylmaleimide,methyl methacrylate,and acrylonitrile

Terpolymers of N‐cyclohexylmaleimide, methylmethacrylate, and acrylonitrile (AN) at different AN feed content were synthesized by suspension polymerization. The thermal properties of the terpolymers such as glass transition temperature (T_g) and Vicat softening temperature (T_Vicat) were determined by torsion braid analysis and Vicat softening temperature tester, respectively. The value of T_g and T_Vicat decreased with increasing AN feed content. Thermogravimetric analyses were carried out with the results that the incorporated AN units enhanced the thermal stability of the resulting polymers and a second degradation step appeared with the addition of AN. The mechanical properties (tensile strength and impact strength) of the terpolymers were also detected and the results show that the tensile strength and impact strength of terpolymers increase with increasing AN feed content. The rheological results illustrated that the terpolymers showed rheological behavior similar to that of pseudoplastic liquid. The apparent shear viscosity decreased with the increasing of AN feed content. The flow power index n increased with increasing AN feed content. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 792–796, 2007     

Synthesis and aqueous solution behavior of hydrophobically modified polyelectrolytes

The hydrophobically modified polyelectrolytes were prepared by a micellar technique from acrylamide, n‐alkylacrylamides, and a third monomer, sodium acrylate or sodium 2‐acrylamide‐2‐methylpropanesulfonate. Synthesis and solution properties of the terpolymers were studied. In the synthesis process, the type and amount of surfactant and anionic monomers influenced their solution behavior greatly. The terpolymers showed strong synergistic viscosification effects between their ions and hydrophobic groups. Their aqueous brine solutions exhibit high viscosity at low polymer concentration and can maintain the viscosity during aging at a high temperature (80°C). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3552–3557, 2001     

Synthesis of block terpolymers of N-methyl methacrylamide with styrene and isoprene by living radical polymerization

The synthesis of block terpolymers of N-methyl methacrylamide (NMeMA) with styrene (St) and isoprene (Is) [poly(NMeMa-b-St-b-Is) and poly(NMeMA-b-Is-b-St)] was achieved by using heterogeneous living radical polymerization (di-t-butylperoxide–UV, benzene) and high vacuum techniques. The existence of living macroradicals was detected by electron paramagnetic resonance (EPR) spectroscopy. The terpolymers were not soluble in common organic solvents. The formation of polymeric blocks was confirmed by modulated differential scanning calorimetry (MDSC) and IR spectroscopy. © 1998 Society of Chemical Industry.     

Synthesis and characterization of new 4‐tolyldiphenylamine derivatives for hole transporting polymers

New hole transport polymers have been synthesized by condensation polymerization of 4‐tolyldiphenylamine (TDPA) with various types of aldehyde. The reaction conditions have been investigated to yield polymers with high molecular weight. It is found that the molecular weight and yield of the TDPA–aldehyde polymers strongly depend on the electron donor–acceptor nature of the substituent on the aromatic ring of the aldehyde monomer. Structural characterization by ¹H NMR spectroscopy shows that the addition condensation reaction occurs exclusively at the para position of TDPA. The electrochemical and optical properties of polymers have been investigated by cyclic voltammetry and UV–vis spectroscopy. Cyclic voltammograms of all polymers show well‐defined pairs of reduction and oxidation peaks, indicating that the polymers are electrochemically active. All polymers show low conductivities of magnitude 10^?14 S cm^?1. Differential scanning calori‐metry measurements reveal that TDPA–aldehyde polymers exhibit glass transitions in the range 170–230 °C. These polymers possess good solubility and the films show sufficient morphological stability. © 2001 Society of Chemical Industry     

Synthesis of branched benzoxazine monomers with high molecular mass,wide processing window,and properties of corresponding polybenzoxazines

Four cyclotriphosphazene‐based benzoxazine monomers (I, II, III, and IV) with relatively high molecular weight were synthesized by a nucleophilic substitution reaction, and their chemical structures were confirmed by ¹H‐NMR and ³¹P‐NMR. A new term, oxazine value (OV, similar to epoxy value), was first proposed to explain the structure–property relationship of the cured polymers. The polymerization behaviors of the four monomers were studied by differential scanning calorimetry and Fourier transform infrared spectroscopy. The maximum exothermic peaks of the four monomers are in the range 244–248 °C. All monomers possess a wide processing window despite their high molecular weight. The thermal stability, glass‐transition temperature (T_g), and mechanical properties of each cured polymer were studied by thermogravimetric analysis and dynamic mechanical thermal analysis. The char yield at 850 °C, T_g, and storage moduli of PIV (polybenzoxazine obtained from monomer IV) are 60.0%, 218 °C, and 9.0 GPa, respectively. The surface property and humidity absorption character of the cured polybenzoxazines were also studied. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44453.     

Graft copolymerization of PU membranes with acrylic acid and crotonic acid using benzoyl peroxide initiator

To improve water wettability of polyurethane (PU), graft copolymerization with acrylic acid (AA) and crotonic acid (CA) was performed using a benzoyl peroxide (BO) initiator. The grafting reaction was carried out by placing the membranes in aqueous solutions of AA and CA at constant temperatures. Variations of graft yield with time, temperature, initiator, and monomer concentrations were investigated. The optimum temperature, polymerization time, monomer, and initiator concentrations for AA were found to be 70°C; 3 h; 1.5 M; 5.0 × 10^?2 M, and for CA 70°C; 1 h; 1.5 M; 4.0 × 10^?2 M, respectively. The grafting membranes were characterized by FTIR spectroscopy and scanning electron microscopy (SEM) analysis, and the effect of grafting on equilibrium water content (EWC) of PU membranes was obtained by swelling measurements. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 2690–2695, 2001     

Preparation of high molecular weight poly(vinyl pivalate) with high yield and high molecular weight poly(vinyl alcohol) by emulsion polymerization of vinyl pivalate and saponification

To prepare high molecular weight (HMW) poly(vinyl pivalate) (PVPi) with high yield and high linearity which is a promising precursor for syndiotactic poly (vinyl alcohol) (PVA), vinyl pivalate (VPi) was emulsion polymerized, using 2,2′‐azobis(2‐amidinopropane) dihydrochloride (AAPH) as an initiator and sodium dodecyl sulfate (SDS) as an emulsifier. The effect of the polymerization conditions on the conversion, molecular weight, and degree of branching was investigated. PVA with maximum number‐average degree of polymerization (P_n) of 6200 could be prepared by complete saponification of PVPi, with P_n of 13,300–16,700 obtained at polymerization temperature of 50°C, using SDS and AAPH concentration of 2.0 × 10^?3 mol/L of water and 1.0 × 10^?3 mol/L of water, respectively, and the maximum conversion was about 90%. From the emulsion polymerization of VPi, spherical PVPi with high yield was effectively prepared, which might be useful for the precursor of syndiotactic PVA micro‐ and nano‐spheres with various surface properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 410–414, 2007     

Initiator‐fragment incorporation radical polymerization of diallyl phthalate: Kinetics,formation of hyperbranched polymer,and iridescent porous film thereof

Diallyl phthalate (DAP) was polymerized in toluene using dimethyl 2,2′‐azobisisobutyrate (MAIB) of high concentrations (0.1–0.9 mol/L) as initiator. The polymerization of DAP of 1.50 mol/L with MAIB of 0.50 mol/L proceeded homogeneously at 80°C without gelation to give soluble polymers in a high yield of 93%. Kinetic results of the homogeneous polymerization at 80°C suggest significant contributions of the degradative chain transfer and the primary radical termination as shown by the rate equation, R_p = k [MAIB]^0.8[DAP]^1.0 (R_p = polymerization rate). The polymer formed in the polymerization of DAP (1.30 mol/L) with MAIB (0.50 mol/L) at 80°C for 8 h consisted of the DAP units with (17 mol %) and without (47 mol %) double bond and the methoxycarbonylpropyl group (36 mol %) as MAIB‐fragment. The large fraction of the incorporated initiator‐fragment as terminal group indicates that the polymer has a hyperbranched structure. The film cast from a solution of the hyperbranched poly(DAP) in tetrahydrofuran showed an iridescent color. The confocal scanning laser microscope image of the film revealed that the iridescent film contained the pores of about 1 μm arranged in an ordered array. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 408–415, 2006     

Investigation of microstructure of the acrylonitrile‐styrene‐glycidyl methacrylate terpolymers by 1D and 2D NMR spectroscopy

Acrylonitrile‐styrene‐glycidyl methacrylate (N/S/G) terpolymers were prepared by bulk polymerization by using benzoyl peroxide as initiator and analyzed by NMR spectroscopy. The compositions of terpolymers were determined by quantitative ¹³C{¹H}‐NMR spectra and compared with those calculated by Goldfinger's equation by using comonomer reactivity ratios: r_NS = 0.04, r_SN = 0.40; r_NG = 0.22, r_GN = 1.37; r_SG = 0.44, r_GS = 0.53. The ¹³C{¹H}‐ and ¹H‐NMR spectra were overlapping and complex. The spectral assignments were done with the help of distortionless enhancement by polarization transfer and two‐dimensional ¹³C‐¹H heteronuclear single quantum correlation experiments. 2D total correlated spectroscopy was used to ascertain the various coupling between the protons. The methyl, methine, methylene, and oxymethylene carbon resonances showed compositional sensitivity. 2D nuclear Overhauser enhancement spectroscopy (NOESY) experiment was used to ascertain the spatial proton–proton couplings. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1779–1790, 2003     

Preparation of superabsorbent polymer hydrogels from trialkyl‐4‐vinylbenzyl phosphonium chloride–acrylamide–methylenebisacrylamide terpolymers and their properties

Superabsorbent polymer gels were synthesized by terpolymerization of three kinds of tri‐n‐alkyl‐4‐vinylbenzyl phosphonium chloride (TRVB) with alkyl chains of different lengths, with acrylamide (AAm), and with N,N′‐methylenebisacrylamide (MBAAm). The water‐absorption ability and antibacterial activity of the gels against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were investigated. The water content of TRVB–AAm–MBAAm terpolymers increased with increasing phosphonium groups in the terpolymers, while the water content decreased with increasing chain length of alkyl groups in the phosphonium groups as well as an increasing degree of crosslinking in the terpolymers. The water content of the terpolymers was depressed by the addition of NaCl. The degree of effect of NaCl addition became higher as the chain length of alkyl groups in the phosphonium groups of the terpolymers became longer. The tri‐n‐octyl‐4‐vinylbenzyl phosphonium chlorides (TOVB)–AAm–MBAAm terpolymers exhibited high antibacterial activity against S. aureus and E. coli in deionized water. The antibacterial activity decreased in 0.9 wt % NaCl solution. The antibacterial activity of TOVB–AAm–MBAAm terpolymers with almost the same phosphonium content increased with the increasing swelling ratio of the terpolymers. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1833–1844, 2000     

Preparation and Characterization of Thermal and pH Dual Sensitive Hydrogel Based on 1,3-Dipole Cycloaddition Reaction

In this study, thermal and pH dual sensitive hydrogels were prepared via Cu-free 1,3-dipole cycloaddition between two copolymers which were modified by azide and maleimide functional groups, respectively. First, the thermally sensitive terpolymers were fabricated via conventional free-radical polymerization of N-isopropylacrylamide, hydroxyethyl methacrylate (HEMA), and N,N-dimethylacrylamide (DMA). Then, polymeric dipolarophiles were synthesized via the esterification between the above terpolymers and N-maleoyl alanine. Similarly, the pH-sensitive terpolymers were also fabricated via conventional free-radical polymerization of 4-vinylpyridine, HEMA, and DMA, and then, polymeric dipoles were acquired via the decoration of the as-prepared terpolymers with 2-azidoacetic acid. Afterward, the smart hydrogels were fabricated via the aqueous 1,3-dipole cycloaddition reaction between the as-prepared polymeric dipolarophiles and dipoles without the use of catalysts. The results of swelling measurements confirm that the hydrogels possessed thermal and pH dual sensitivity. Moreover, the investigation of the behavior of oscillatory swelling shrinking indicates their sensitivity to temperature and pH was reversible and repeatable, which is of great significance for the repeated use of the prepared hydrogels. The proposed strategy demonstrates a great application prospects in the preparation of hydrogels as there were no catalysts and organic solvents employed. POLYM. ENG. SCI., 60:917–924, 2020. © 2020 Society of Plastics Engineers     

Correlation of binder mechanical properties with microstructure for poly(butadiene–acrylonitrile–methacrylic acid) terpolymer: 13C-NMR and pyrolysis-GC studies

¹³C-NMR spectroscopy (22.5 MHz) was used to characterize poly(butadiene (B)–acrylonitrile (A)–methacrylic acid (M)) liquid terpolymers prepared by emulsion polymerization. The sequence distribution of the monomers in the terpolymers was described in terms of triads BBB, ABA, ABB, BBA, MBB, and AMB and was found to vary with the mode of addition of methacrylic acid monomer. The NMR data was found to be in good agreement with a mechanism of polymerization in which methacrylic acid is preferentially involved in initiation reactions by a thiyl radical arising from the reaction of the chain modifier, 1-dodecanethiol, and cyanoisopropyl radical generated from AIBN initiator. Binders obtained by curing the liquid terpolymers with an epoxy resin showed widely varying mechanical properties with tensile strength varying from 4.3 to 0.6 kg/cm² and elongation at break from 130 to 450%. It was found that tensile strength increases and elongation decreases with the number of acrylonitrile units between the methacrylic acid crosslinks. Good correlation was obtained between triad population ratio [ABB + BBA] [BB^vB]/[ABA][MBB] and the mechanical properties of the binders. Pyrolysis-GC data at 550 and 600°C confirmed the results obtained from ¹³C-NMR, and the mole ratio of butadiene to arylonitrile in the pyrolyzates showed correlation with the properties of binders.     

Preparation and characterization of poly(p-phenylenediamine-co-xylidine)

p-Phenylenediamine (PPDA) homopolymer and its copolymers with 2,3-xylidine (XY) were synthesized by oxidative polymerization using potassium persulfate as an oxidant in HCl medium at room temperature. The yield, intrinsic viscosity, and solubility of the polymers were significantly dependent on the monomer ratio. The resulting polymers were characterized by Fourier transform IR spectroscopy, ¹H-NMR spectroscopy, wide-angle X-ray diffraction, and thermogravimetry methods. The results showed that the number-average degree of polymerization of the PPDA homopolymer was 33 and the actual content of XY units in the copolymer was slightly higher than the feed XY unit content. The polymers were substantially amorphous and showed the strongest diffraction at a Bragg angle of 3°. The polymers exhibited a thermal decomposition temperature higher than 436°C, the maximum weight-loss rate was slower than 4%/min, and the char yield was larger than 24 wt % at 600°C in nitrogen. The activation energy of thermal decomposition for the polymers increased from 19 to 25 kJ/mol with increasing XY unit contents from 0 to 10 mol %. The polymers showed higher thermostability but lower activation energy of decomposition in nitrogen than in air. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3107–3116, 2001