Natural abundance 15n solid‐state nmr study of nylon‐6 in blends

Natural abundance solid‐state nuclear magnetic resonance spectroscopy (NMR) of nitrogen‐15 (¹⁵N) was applied to investigate the films of nylon‐6 and their blends with poly(propylene oxide) (PPO). The NMR ¹⁵N results allowed us to identify the crystalline forms present in these blends and also confirmed the previous NMR results obtained by ¹³C‐NMR study. From all NMR data the antiplasticization phenomena and plasticization effects caused by PPO content, in the blends were characterized. The polyoxide action is a function of its proportion. However, because the samples were prepared by solution casting, the residual solvent action cannot be ignored. The ¹⁵N chemical shift changes were influenced by both PPO and residual solvent. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3872–3875, 2003     

Solid‐state NMR characterization of cyclomaltoheptaose (β‐cyclodextrin) polymers using high‐resolution magic angle spinning with gradients

Solid‐state nuclear magnetic resonance (NMR) techniques were used to characterize cyclomaltoheptaose (β‐cyclodextrin, β‐CD) polymers. These insoluble materials have been investigated by cross‐polarization magic angle spinning with dipolar decoupling (CP/MAS), magic angle spinning without dipolar decoupling (MAS), and high‐resolution magic angle spinning with gradients (HRMAS). These NMR spectra allow the assignment of the principal ¹H and ¹³C signals. The presence of two distinct components (cross‐linked β‐CD and polymerized epichlorohydrin) in the materials was clearly demonstrated. These polymers were used as sorbents and the resulting NMR spectra are presented and discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 1288–1295, 2000     

Effects of EPDM‐g‐MAH compatibilizer and internal mixer processing parameters on the properties of NR/EPDM blends: An analysis using response surface methodology

This study evaluates the effects of ethylene‐propylene‐diene‐monomer grafted maleic anhydride (EPDM‐g‐MAH) and internal mixer melt compounding processing parameters on the properties of natural rubber/ethylene‐propylene‐diene rubber (NR/EPDM) blends. Using Response Surface Methodology (RSM) of 2⁵ two‐level fractional factorial, we studied the effects of NR/EPDM ratio, mixing temperature, Banbury rotor speed, mixing period, and EPDM‐g‐MAH contents in NR/EPDM blends. The study found that the presence of EPDM‐g‐MAH in NR/EPDM blends had a predominant role as a compatibilizing agent, which affected the processability and properties of the final material. We also determined the model fitting with constant determination, R² of 99.60% for tensile strength (TS) response with a suggested combination of mixing process input parameters. The reproducibility of the proposed mixing strategy was then confirmed through model validation with a minor deviation at +2.303% and higher desirability of 0.960. This study is essential in providing a process design reference for NR/EPDM blends preparation by melt‐blending and the role of a compatibilizer from the systematic Design of Experiment (DOE) approach. The experimental findings were further supported with swelling and cross‐link density measurements, differential scanning calorimetry analysis, and observation of fracture morphology using a scanning electron microscope. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42199.     

Cross‐linking of polybutadiene: correlation between solid‐state 1H NMR spectroscopy,thermoporosimetry, densimetry and crystallinity measurements

T₂ proton NMR relaxation times were used to follow the changes in the macromolecular chain mobility of a chemically (by dicumyl peroxide) cross‐linked polybutadiene matrix. The same phenomenon was also studied by an investigation of the ability of the polymer to crystallize using DSC measurements. The solubility of the elastomer depends on the size of its macromolecular chains. Cross‐linking, leading to an increase in the size of macromolecules, provokes an insolubility of the elastomer. By densimetry measurements, it was possible to follow the changes in the solubility of the polymer up to its gel‐point. Beyond the gel‐point, the swelling solvent, cyclohexane, was used as a textural probe. Using the shift of its solid‐solid thermal transition points, it was possible to calculate the distribution of the distances between the cross‐links as a function of the curing times by thermoporosimetry analysis. Copyright © 2003 Society of Chemical Industry     

Segmental orientation of thermoplastic polyurethanes investigated by 1H double-quantum NMR. Correlation with thermodynamic and mechanical properties

The segmental orientation of a series of thermoplastic polyurethane (TPU) samples with different content in hard segments and different number average molecular weights of soft segments was investigated by ¹H double-quantum (DQ) NMR. The residual dipolar couplings of the hard segments were measured via the residual second van Vleck moments. A simple theoretical approach based on Rouse modes was developed to explain the orientation dependence of the hard segments on the number average molecular weight of the soft segments. The effective transverse relaxation rates of the hard segments were correlated to the ¹H residual dipolar couplings. Moreover, the correlation between the segmental orientation of the hard segments and the thermodynamic and mechanical properties of the TPU samples is investigated. The glass transition temperatures of the soft segments represent the relevant thermodynamic quantities. The mechanical parameters used for discussing the correlations are Young's modulus, yield stress, and rebound resilience angles from tensile testing and rebound resilience measurements.     

Synthesis and properties of sulfonated poly(phosphazene)‐graft‐poly(styrene‐co‐N‐benzylmaleimide) copolymers via atom transfer radical polymerization for proton exchange membrane

A series of sulfonated poly(phosphazene)‐graft‐poly(styrene‐co‐N‐benzylmaleimide) (PP‐g‐PSN) copolymers were prepared via atom transfer radical polymerization (ATRP), followed by regioselective sulfonation which occurred preferentially at the poly(styrene‐co‐N‐benzylmaleimide) sites. The structures of these copolymers were confirmed by Fourier transform infrared (FTIR) spectroscopy, ¹H‐NMR, and ³¹P‐NMR, respectively. The resulting sulfonated PP‐g‐PSN membranes showed high water uptakes (WUs), low water swelling ratios (SWs), low methanol permeability coefficients, and proper proton conductivities. In comparison with non‐grafting sulfonated poly(bis(phenoxy)phosphazene) (SPBPP) membrane previously reported, the present membranes displayed higher proton conductivity, significantly improved the thermal and oxidative stabilities. Transmission electron microscopy (TEM) observation showed clear phase‐separated structures resulting from the difference in polarity between the hydrophobic polyphosphazene backbone and hydrophilic sulfonated poly(styrene‐co‐N‐benzylmaleimide) side chains, indicating effective ionic pathway in these membranes. The results showed that these materials were promising candidate materials for proton exchange membrane (PEM) in direct methanol fuel cell (DMFC) applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42251.     

Damping elastomer with broad temperature range based on irregular networks formed by end‐linking of hydroxyl‐terminated poly(dimethylsiloxane)

Irregular networks based on the condensation reaction of hydroxyl‐terminated poly(dimethylsiloxane) with cross‐linkers were investigated. The networks have excellent damping properties in a wide temperature range utilizing the viscoelastic relaxation of the irregular network with dangling chains. NMR Cross‐link Density Spectroscopy was used to explore the weight fraction of pendant chains and elastic chains in the elastomer. The transverse relaxation time for the elastomer was studied to explore the influence of pendant chains. The effects of the structure of cross‐linkers and the molecular weight of precursors were studied in detail. Elastomers cross‐linked by tetra‐functional cross‐linker (TEOS) have higher damping properties than the elastomers cross‐linked by tri‐functional cross‐linkers (MTMS and OTMS). A damping elastomer based on irregular networks with effective damping (tanδ > 0.3) temperature range of more than 250°C (from lower than ?60°C to 190°C) was prepared. POLYM. ENG. SCI., 56:97–102, 2016. © 2015 Society of Plastics Engineers     

Miscibility and transesterification in ternary blends of poly(ethylene naphthalate)/poly(pentamethylene terephthalate)/poly(ether imide)

Miscibility and morphology of poly(ethylene 2,6‐naphthalate)/poly(pentamethylene terephthalate)/poly(ether imide) (PEN/PPT/PEI) blends were studied by differential scanning calorimetry (DSC), optical microscopy (OM), proton nuclear magnetic resonance imaging (¹H‐NMR), and wide‐angle X‐ray diffraction (WAXD). OM and DSC results from ternary blends revealed the immiscibility of PEN/PPT/PEI blends, but ternary blends of all compositions were phase‐homogeneous following heat treatment at 300°C for over 60 min. Annealing samples at 300°C yielded an amorphous blend with a clear and single T_g at the final state. Experimental data from ¹H‐NMR revealed that PEN/PPT copolymers (ENPT) were formed by the so‐called transesterification. The effect of transesterification on glass transition and crystallization was discussed in detail. The sequence structures of the copolyester were identified by triad analysis, which showed that the mean sequence lengths became shorter and the randomness increased with heating time. The results reveal that a random copolymer improved the miscibility of the ternary blends, in which, the length of the homo segments in the polymer chain decreased and the crystal formation was disturbed because of the irregularity of the structure, as the exchange reaction proceeded. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3840–3849, 2006     

Peroxide induced cross‐linking by reactive melt processing of two biopolyesters: Poly(3‐hydroxybutyrate) and poly(l‐lactic acid) to improve their melting processability

Poly(3‐hydroxybutyrate) (PHB) and poly(l ‐lactic acid) (PLLA) were individually cross‐linked with dicumyl peroxide (DCP) (0.25–1 wt %) by reactive melt processing. The cross‐linked structures of the polymer gel were investigated by nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectroscopies. The size of the polymer crystal spherulites, glass transition temperature (T_g), melting transition temperature (T_m), and crystallinity were all decreased as a result of cross‐linking. Cross‐linking density (ν_e) was shown to increase with DCP concentration. Based on parallel plate rheological study (dynamic and steady shear), elastic and viscous modulus (G″ and G′), complex viscosity (η^*) and steady shear viscosity (η) were all shown to increase with cross‐linking. Cross‐linked PHB and PLLA showed broader molar mass distribution and formation of long chain branching (LCB) as estimated by RheoMWD. Improvements in melt strength offer bioplastic processors improved material properties and processing options, such as foaming and thermoforming, for new applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41724.     

Effects of molecular weight on phase structure of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) blends

The phase structure of poly(ethylene terephthalate)/poly(ethylene 2,6‐naphthalate) (PET/PEN) blends was studied in relation to the molecular weight. The samples were prepared by both solution blends, which showed two glass‐transition temperatures (T_g), and melt blends (MQ), which showed a single T_g, depending on the composition of the blends. The T_g of the MQ series was independent of the molecular weight of the homopolymer, although the degree of transesterification in the blends was affected by the molecular weight. The MQ series showed two exotherms during the heating process of a differential scanning calorimetry scan. The peak temperature and the heat flow of the exotherms were affected by the molecular weight of the homopolymers. The strain‐induced crystallization of the MQ series suggested the independent crystallization of PET and PEN. Based on the results, a microdomain structure of each homopolymer was suggested. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 2428–2438, 2005     

The Cross‐Linking Effect on the Thermoelectric Properties of Conjugated Polymer/Carbon Nanotube Composite Films

Composite insulating organic material with conducting inorganic nanomaterial is a promising way to compensate the electrical conductivity, which is a prerequisite for the practical realization of the organic thermoelectrics. It is demonstrated that organic–inorganic interfacial interactions play critical rules for composites' thermoelectric performance. Here, an alternative interfacial engineering approach is proposed; that is, post‐blending cross‐linking of conjugated polymers (CPs). CPs substituted by exo‐olefin side chains that can form covalent cross‐linking via ruthenium‐catalyzed olefin metathesis are newly designed and synthesized. Pre‐cross‐link CP/single‐walled carbon nanotube (SWCNT) composites exhibit relatively high power factor that reach up to 70.3 µW m^?1 K^?2. It is found that the cross‐linking process, using second generation Grubbs reagent, is detrimental to the thermoelectric performance. Cross‐linked composites exhibit much lower power factor (0.77–19.7 µW m^?1 K^?2) mainly due to the low electric conductivity of the samples, while there is no significant change in Seebeck coefficient. It may be because the formation of tightly cross‐linked network hinders the transport of carriers in CP/SWCNT, resulting in a significant decrease in the electric conductivity. These structure–property relationship studies provide useful guidelines for designing organic thermoelectric materials with performance improvement and applied green processing.     

Novel polyethylene‐b‐polyurethane‐b‐polyethylene triblock copolymers: Facile synthesis and application

A series of novel polyethylene‐b‐polyurethane‐b‐polyethylene (EUE) triblock copolymers is successfully prepared through a facile route combining the thiol‐ene chemistry, addition polymerization, and coupling reaction. The resulting EUE triblock copolymers are characterized by Nuclear magnetic resonance (¹H NMR), Fourier transform‐infrared spectra (FT‐IR), High temperature gel permeation chromatography (HT‐GPC), Differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), and Transmission electron microscopy (TEM). In addition, the EUE triblock copolymers have been evaluated as compatibilizers in the polymer blends of thermoplastic polyurethane elastomer (TPU) and high‐density polyethylene (HDPE). The SEM results show that the compatibility of immiscible blends is enhanced greatly after the addition of EUE triblock copolymers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42967.     

Electron‐beam irradiation of blends of polypropylene with recycled acrylonitrile‐butadiene rubber

One‐mm thick sheets were prepared from blends of polypropylene and recycled acrylonitrile‐butadiene rubber (rNBR) with different blend ratios. Trimethylolpropane triacrylate (TMPTA) was used as a co‐agent. Electron‐beam‐initiated cross‐linking of the sheets was carried out at a dose of 40 kGy, and 3 phr of TMPTA based on the weight of rNBR was used. Properties such as tensile strength, Young's modulus, elongation at break, swelling percentage in oil, and morphology were studied. The results showed that the tensile properties had been improved by irradiation. The studies of swelling in oil revealed a higher cross‐link density in the irradiated blends compared to that in nonirradiated blends at similar blend ratios. Scanning electron microscopy studies revealed better adhesion between the phases and rough failure surfaces with a large number of tear lines which indicated a higher energy requirement for the failure of irradiated blends compared to that for nonirradiated blends. J. VINYL ADDIT. TECHNOL., 2010. © 2010 Society of Plastics Engineers     

Organic solvent absorbents based on linear diol

Cross‐linked poly(orthocarbonate)s were prepared by condensation of the tetraethyl orthocarbonate with different length of aliphatic diols. The synthesized polymers have been characterized by Fourier‐transform infrared spectroscopy, solid‐state ¹³C cross‐polarization magic angle spinning (CPMAS) nuclear magnetic resonance, thermal gravimetric analysis, and elemental analysis. The cross‐linked polymers were evaluated for organic solvent absorbency application. The effect of diol type on swelling properties of cross‐linked polymers was studied through the solvent absorption tests. The swelling parameters such as maximum solvent absorbency, saturation time, and retention of the solvent were evaluated for the synthesized sorbents. All of the cross‐linked polymers had moderate thermal stability and good regenerable solvent uptake abilities. POLYM. ENG. SCI., 53:2102–2108, 2013. © 2013 Society of Plastics Engineers     

Preparation,structure characterization,and thermal performance of phenyl‐modified MQ silicone resins

Methyl‐ and phenyl‐modified MQ resins have been prepared by cohydrolysis and condensation‐polymerization of the prepolymer of sodium silicate with SiO₂/Na₂O = 3.33 using the ethanol solution of hexamethyldisiloxane (MM), 1,1,3,3‐tetramethyl‐1,3‐divinyldisiloxane (TMDVS), methyldiphenylethoxysilane (MDPES), dimethylphenylethoxysilane (DMPES), or their dimers. The influence of different end‐capping agents on the composition and properties of the MQ resins has been investigated. Thermogravimetric analysis and differential scanning calorimetry results indicate that when the MQ resins are end capped with DMPES instead of MDPES, the resins were more easily purified and almost no high boiling point residuals were found in the phenyl MQ resins. The refractive indexes of the MQ resins were significantly affected by the phenyl group and their values could be adjusted by changing the amount of DMPES. The structures of the resins were characterized by ¹H‐NMR and FT–IR spectroscopy. The M/Q ratios in the prepared MQ resins were calculated from the ¹H‐NMR spectra or from elemental analysis or both. The M/Q values obtained agreed well with the changes of appearance and thermal stabilities of the MQ resins. The thermal stabilities of the MQ resins were greatly enhanced when DMPES was used. Phenyl‐modified MQ resins were in the form of white powders due to the rigidity of the phenyl group while methyl MQ resins exhibited a range of appearances, from transparent liquids to white powders, with the reduction of M/Q values. The method developed to calculate the M/Q values is useful for the characterization of MQ resins and their derivatives. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Modification of SPPESK proton exchange membranes through layer‐by‐layer self‐assembly

Sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) composite membranes are fabricated through electrostatic layer‐by‐layer (LbL) self‐assembly method with chitosan (CS) and phosphotungstic acid (PWA) to enhance the proton conductivity and stability. The results demonstrate that LbL self‐assembly has different effects on the SPPESK membrane substrates with different sulfonation degrees (DSs). It elevates proton conductivity of the SPPESK membrane of lower DS and enhances swelling stability of the SPPESK membrane of higher DS. For instance, at 80°C, proton conductivity of the SPPESK0.74/(CS/PWA)₁ membrane (lower DS) increases by 16%–96.49 mS cm^?1, and swelling ratio of the SPPESK1.01/(CS/PWA)₃ membrane (higher DS) decreases from 58 to 29%. Attribute to the electrostatic interaction and ion cross‐linking networks, permeability of the SPPESK0.74/(CS/PWA)₃ membrane and the SPPESK1.01/(CS/PWA)₅ membrane are reduced by 45 and 30%, respectively. The results indicate that the LbL self‐assembly has broadened the available DS range for fuel cell applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 132, 42867.     

Surface functionalization of rubber latex nanoparticles with sulfidosilane moieties

Polybutadiene latex particles were functionalized with bis[3‐(triethoxysilyl) propyl] tetrasulfide (TESPT) in the presence of zinc oxide as an activator and ethanol as a co‐solvent. The success of this reaction was confirmed both by the peaks attributed to Si‐O groups at 1085 and 1110 cm^?1 and C‐S bond at 630 cm^?1 which appeared after reaction in Attenuated Fourier Transform Infrared (ATR‐FTIR) Spectra and also by increasing in the particle size diameter of latex particles (from 95 to 127 nm) in Dynamic Light Scattering analysis. X‐ray Diffraction results also showed changes in crystalline structure of the modified particles (as a strong decrease in the intensity of peak at 2θ=19.54). The effect of reactant concentration in a constant amount of TESPT (by varying the water and ethanol content), reaction time, activator size (micro and nanoparticles), and pH (≈7, 8.5) were investigated on degree of grafting (obtained from thermogravimetric analysis and ATR‐FTIR spectra), particle size diameter, cross‐link density, and swelling ratio of the samples. The amounts of silane grafting and cross‐link density of polymer particles were increased by an increase in the reaction time. The highest grafting degree was observed at low concentration of TESPT. Silane functionalization was also improved in a slight basic condition (pH=8.5) rather than neutral pH. The grafting reaction took place such as sulfur pre‐vulcanization and the possible mechanism of this reaction was discussed. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43268.     

NMR study of poly(vinylpyrrolidone)/poly(ethylene oxide) blends

Development of polymeric blends has become very important for polymer industries because they have been shown to be successful and versatile alternatives to obtain new polymers. In this work binary blends formed by poly(vinylpyrrolidone) (PVP) and poly(ethylene oxide) (PEO) were studied by solution and solid‐state NMR to determine their physical interaction, homogeneity, and compatibility for use as membranes to separate water/alcohol. The NMR results allowed us to acquire information on the microstructure and molecular dynamic behavior of polymer blends. From the NMR solution it was possible to evaluate the microstructure: PVP presented a preferential syndiotactic distribution sequence and PEO presented two regions, one crystalline and the other amorphous. Considering the solid‐state NMR results it was possible to evaluate the molecular dynamics and all binary blends, showing that PEO behaves as a plasticizer; some intermolecular interaction was also observed. An important point was to evaluate the microstructure of the carbonyl PVP using cross polarization/magic‐angle spinning (CP/MAS) and CP/MAS/dipolar decoupling that was not observed before. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2820–2823, 2002     

Synthesis of carbazole‐substituted poly(dimethylsiloxane) and its improved refractive index

A series of substituted 9‐vinylcarbazole polysiloxane was synthesized followed by room temperature vulcanization to afford a crosslink network via trimethoxysilane crosslinker. Structural confirmation was made using FTIR, one and two‐dimensional ¹H‐ and ²⁹Si‐NMR spectroscopy. Quantitative estimation of the amount of substituted carbazole was made based on NMR data. These were related to the refractive index whose values were in the range of 1.4370–1.4625 at increasing carbazole content. These values are higher than uncrosslink series, attributable to the tightness of the systems. They displayed an improved thermo‐optic coefficient compared to linear unsubstituted polydimethylsiloxane (PDMS). The synergistic effect of substituted carbazole unit with the crosslink network of PDMS presents a viable choice of encapsulant for opto‐electronic devices. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41654.     

Analysis of low‐density polyethylene‐g‐poly(vinyl chloride) copolymers formed in poly(vinyl chloride)/low‐density polyethylene melt blends with gel permeation chromatography and solid‐state 13C‐NMR

Gel permeation chromatography (GPC) and solid‐state ¹³C‐NMR techniques were used to analyze the structural changes of poly(vinyl chloride) (PVC) in blends of a low‐density polyethylene (LDPE) and PVC during melt blending. The GPC results showed that the weight‐average molecular weight (M_w) of PVC increased with LDPE content up to 13.0 wt % and then decreased at a LDPE content of 16.7 wt %, whereas the number‐average molecular weight remained unchanged for all of LDPE contents used. The ¹³C‐NMR results suggest that the increase in M_w was associated with the formation of a LDPE‐g‐PVC structure, resulting from a PVC and LDPE macroradical cross‐recombination reaction during melt blending. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3167–3172, 2004