Basic structure–property behavior of polyurethane cationomers

Polyurethane (PU) cationomers were synthesized from polytetramethylene adipate glycol (PTAd), isophorone diisocyanate (IPDI), and N-methyl diethanolamine (MDEA) according to a prepolymer mixing process. Basic structure-property behavior of the emulsion (obtained by adding water to the ionomer solution) and emulsion cast film was studied with regard to the molecular weight (M_n) of PTAd, MDEA content, degree of neutralization, and extender functionality. Particle size decreased asymptotically with increasing M_n of PTAd due to the increased chain flexibility, and with the degree of neutralization due to the increased hydrophilicity of the PU. Emulsion viscosity generally showed the opposite tendency with particle size dependence. The major transition temperature, corresponding to the glass transition (T_g) of phase mixed PU or hard segment-rich phase of the PU monotonically increased with MDEA content, degree of neutralization, and with increasing extender functionality. However, with increasing M_n of PTAd, T_g first decreased (M_n = 1000) and then increased (M_n = 1500, 2000), due respectively to the increased hard fraction of phase mixed PU, and soft segment crystallization. Tensile strength increased and elongation at break decreased with MDEA content, degree of neutralization, and extender functionality. © 1994 John Wiley & Sons, Inc.     

Quantitative structure–property relationships in the pyridine series

By means of the MNDO, AM1, and PM3 methods, standard heats of formation, entropies, ionization potentials, and molecular dipole moments of the pyridine series compounds have been computed. The information on the experimental values of the above quantities has been systematized. Linear dependencies allowing a priori evaluation of thermodynamic and molecular characteristics of pyridines have been stated. Correlations of the 2,2′‐bipyridines pK_a values for aqueous solutions with the gaseous‐phase proton affinities have been found. © 2002 Wiley Periodicals, Inc. Heteroatom Chem 13:229–241, 2002; Published online in Wiley Interscience (www.interscience.wiley.com). DOI 10.1002/hc.10013     

A process–structure–property study of anisotropic PMDA-ODA films

A practical methodology for the correlation and prediction of the process–property performance of advanced materials is developed. The model polymer studied is PMDA-ODA polyimide. The connecting link between the process and the properties is the structural state of the polymer. An essential ingredient for a quantitative characterization of the system is a knowledge of its phase state and intrinsic molecular properties. The intrinsic molecular properties define the limiting performance properties available to the polymer. Anisotropic films and sheets produced by five different fabrication processes are examined. Maps of the molecular symmetry axis, the orientation function, and the thickness distributions of two 50-in.-wide sheets fabricated differently are measured nondestructively for process comparison. Four other film fabrication processes are examined and their three-dimensional orientation states determined and correlated. A three-dimensional orientation function triangular plot permits simultaneous representation of the different fabrication processes on the same figure and allows the investigator to choose the most economic and efficient fabrication route. The structure–property study includes the structural correlation and intrinsic molecular property determination of the anisotropic coefficient of thermal expansion (CTE), the anisotropic mechanical moduli and compliances, and the anisotropic dielectric constants. 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 777–788, 1997     

Chlorine distribution and structure–property relationship of chlorinated polypropylene

High-resolution proton magnetic resonance (PMR) spectroscopy was used to determine the chlorine distribution of chlorinated polypropylenes in 1,1,2,2,-tetrachloroethane solution and suspension (5–25 wt % chlorine). The determination is based on measuring the relative amounts of methyl and methylene groups which are α, β, and γ to chlorinecontaining groups in chlorinated polypropylenes. The results obtained from the 100 MHz and 220 MHz PMR spectrometers were compared with the theoretical predictions provided by Frendsdorff and Ekiner, based on the statistics of substitution polymers. Furthermore, the PMR data were correlated with infrared and differential scanning calorimetry data to obtain the structural and crystalline properties. The comparison showed that the suspension-chlorinated polypropylenes show structure heterogeneity and thermal instability, whereas polymers chlorinated in solution with gaseous chlorine show a random chlorine distribution and thermal stability compared with the former.     

Environmental stress cracking resistance of polyethylene: The use of CRYSTAF and SEC to establish structure–property relationships

Nineteen commercial high‐density polyethylene resins made with different polymerization processes and catalyst types were analyzed by high‐temperature size exclusion chromatography and crystallization analysis fractionation. The information obtained with these characterization techniques on the polymer chain structure was correlated to environmental stress cracking resistance. Environmental stress cracking resistance increases when the molecular weight and concentration of polymer chains that crystallize in trichlorobenzene between 75 and 85 °C increase. Polymer chains present in this crystallization range are assumed to act as tie molecules between crystal lamellae. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1267–1275, 2000     

Influence of the styrene–maleate ratio on the structure–property relationships of unsaturated polyester networks

Several structural series of unsaturated polyester networks which had different isophthalic acid–maleic anhydride ratios or different precentage rates of styrene incorporated in the network were studied by means of thermomechanical tests. It was demonstrated that the transition zone (α and β) did not correspond specifically to a polytyrene phase but could be linked to the presence of microdomains of different structures within the polyester network. It is the successive setting in motion of these microdomains, under the effect of a rise in temperature, which creates a broad transition zone. Structural chain formations based on the resin components (prepolymer and styrene) were proposed and linked to the transition temperatures detected. The improved knowledge of the structure and the various microdomains present within the networks will provide a better apprehension of the hydrolytic stability of unsaturated polyester materials.     

Synthesis and structure–property relationships of acrylic core–shell particle-toughened epoxy networks

The use of emulsion polymerization to prepare core–shell rubber (CSR) toughening particles with different shell thickness-to-core diameter ratios is described. The conditions leading to controlled particle size and morphology are discussed. The particle shell is crosslinked during the synthesis so that its integrity and morphology are maintained upon curing of the epoxy network. The mixing of the CSR particles with the reactive epoxy and the processing of toughened-epoxy networks are described. The characteristics of each phase and the mechanical properties of the materials are reported. The fracture parameters (K_lc, G_lc) are discussed in relation to the structure of the CSR-particles.     

Basic structure–property behavior of UV curable polyurethane acrylates

Effects of hard segment type, soft segment type, soft segment length, and crystallization at various levels of reactive diluent have been studied in polyurethane acrylates. PTMG–IPDI-based PU acrylates gave better soft segment-hard segment phase separation as compared with PTMG–TDI-based ones. Among PTMG–, PCL–, and PTAd–IPDI-based materials, only PTMG-based one gave clean phase separation, and PTAd-based gave the poorest phase separation. With greater phase separation, higher modulus was obtained. Crystallization of soft segment in PTAd–IPDI-based material gave a significant increase in tensile modulus and elongation at break, with a notable difference in dynamic mechanical properties. © 1996 John Wiley & Sons, Inc.     

Azoalkanes—novel flame retardants and their structure–property relationship

A number of symmetrical and unsymmetrical azoalkanes of the general formula R′?N = N?R and related azoxy, hydrazone as well as azine derivatives have been synthesized in order to assess their potential as novel flame retardants for polypropylene alone or in combination with commercially available flame retardants such as alumina trihydrate (ATH), decabromodiphenyl ether (DecaBDE) and tris(3‐bromo‐2,2‐bis(bromomethyl)‐propyl)phosphate (TBBPP). The experimental results show that in the series of different sized azocycloalkanes the flame retardant efficacy decreased in the following order: R = cyclohexyl > cyclopentyl > cyclobutyl > cyclooctanyl >> cyclododecanyl. Whereas in the series of aliphatic azoalkanes compounds the efficacy decreased in the following order: R = n‐alkyl > tert‐butyl > tert‐octyl. In addition, also some of the prepared azoxy, azine, and hydrazone derivatives provide flame retardancy to polypropylene films at already very low concentrations (0.25–1 wt%). Noteworthy is that in contrast to other halogen‐free radical generators, the azoalkanes are also very effective as flame retardants in polypropylene thick moldings. Interestingly, it was found that 4,4′‐bis(cyclohexylazocyclohexyl)‐methane) shows a strong synergistic effect with ATH. Thus, in the presence of 0.5 wt% of azoalkane the ATH loading could be reduced from 60 to 25 wt% and still UL94 V‐2 rating could be reached. Furthermore, the fire testing data reveal that azoalkanes show a synergistic effect with DecaBDE and when used in conjunction with very low loadings of TBBPP. Copyright © 2010 John Wiley & Sons, Ltd.     

Accelerated water tree aging of crosslinked polyethylene with different degrees of crosslinking

The effect of crosslinking degree on accelerated water tree aging in crosslinked polyethylene (XLPE) was investigated. The peroxide-crosslinking process was adopted to make XLPE specimens with different degrees of crosslinking by controlling the doping content of dicumyl peroxide (DCP) in low-density polyethylene (LDPE). The water blade electrode method was applied to accelerate water-tree aging of LDPE and XLPE specimens (hereafter referred to as the specimens), and their morphologies were observed using an optical microscope. The variation of crystalline morphology and anti-cracking performance of the amorphous region in the specimens were analyzed by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and an electronic universal testing machine. Based on the experimental results, it was found that XLPE has great anti-water-treeing performance compared to LDPE. In addition, the higher the crosslinking degree, the better the anti-water-treeing performance. Although crystal growth is inhibited due to the crosslinking reaction, the density of tie molecular chains greatly increases in the amorphous region and exhibits significantly tighter lamellar stacking, which is the reason that water tree growth is restrained with increasing crosslinking degree.     

Synthesis and structure–property relationship of carbazole‐alt‐benzothiadiazole copolymers

A series of four π‐conjugated carbazole‐alt‐benzothiadiazole copolymers (PCBT) were prepared by Suzuki cross‐coupling reaction between synthesized dibromocarbazoles as electron‐rich subunits and 4,7‐bis(4,4,5,5‐tetramethyl‐1,3,2‐dioxaborolan‐2‐yl)?2,1,3‐benzothiadiazole as electron‐deficient subunits. The subunits were directly linked through 2,7‐ or 3,6‐ positions of the carbazole. In addition, the carbazole monomers have been N‐substituted by a branched or a linear side‐chain. The chemical structure of the copolymers and their precursors was confirmed by NMR and IR spectroscopies, and their molar masses were estimated by SEC. Thermal analysis under N₂ atmosphere showed no weight loss below 329°C, and no glass transition was observed in between 0 and 250°C. The band gaps of all PCBTs evaluated by optical spectroscopies and by cyclic voltammetry analysis were consistent with expectations and ranged between 2.2 and 2.3 eV. Finally, 2,7 and 3,6 linkages were shown to influence optical properties of PCBTs. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2059–2068     

Viscoelastic properties and interfacial tension of polystyrene–polyethylene blends

The linear viscoelastic properties of polystyrene polyethylene (PS/PE) blends have been investigated in the molten state. For concentrations of the dispersed phase equal to 30 vol %, the blends exhibited a droplet‐matrix morphology with a volume‐average diameter of 5.5 μm for a 70/30 PS/PE blend at 200 °C and 14.7 μm for a 30/70 PS/PE blend at 230 °C. Enhanced elasticity (G′) for both blends, in the terminal zone, compared to the modulus of the matrix (PS and PE, respectively) was observed. This is related to the deformation of the droplets in the matrix phase and hence to the interfacial forces between the blend components. The results for these uncompatibilized blends are shown to be in agreement with the predictions of the emulsion model of Palierne. These predictions were used to obtain the interfacial tension between PS and PE, which was found to be between 2 and 5 mN/m at 200 °C and 4 ± 1 mN/m at 230 °C. Independent interfacial tension measurements using the breaking‐thread method resulted in a value of 4.7 mN/m and 4.1 mN/m at 200 °C and 230 °C for the respective blends. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1359–1368, 2000     

Temperature‐dependent polymer–polymer interactions in polystyrene–polyethylene blends

The effect of the temperature on the interaction between the components of an immiscible polystyrene–polyethylene blend has been analyzed with different techniques. Lap‐shear‐strength data and morphological observations indicate an enhanced interaction between the polymeric phases at elevated temperatures, at which dispersive forces are known to predominate. This raises the degree of compatibility of the polymeric components. Rheological measurements also justify the concept of increased adhesion between the components of the blend when it is processed at very high temperatures. Differential scanning calorimetry analysis lends support to an improved homogeneity of the blend at an elevated temperature; this is again consistent with an improved interaction between the blend phases. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2545–2557, 2004     

Polyimide structure–property relationships. II. Polymers from isomeric diamines

An extensive study of the effects of stereoisomeric variations in aromatic polyimide structures on polyimide properties was conducted. The structural variations were incorporated into the polyimides through the use of two complete series of isomeric aromatic diamine monomers, the diaminodiphenylmethanes and the diaminobenzophenones, as well as several pairs of diamine isomers. The ability of the diamines to polymerize was related to the basicities, and thus reactivities, of the amino groups. Diamines with an amino group located ortho to the group connecting the two aromatic rings were successfully polymerized with dianhydrides for the first time to high molecular weight poly(amic acids). The stereoisomeric polyimides were characterized by determining the glass transition temperatures T_g, mechanical properties, and thermooxidative stabilities of thin films of the polymers. The polymers prepared from p-diamines were shown to have the highest softening points and thus, the most rigid molecular structures. Those synthesized from m-diamines had the lowest T_g values, inferring the most flexible molecular backbone. With limited exceptions, the use of diamines with ortho-oriented amine groups failed to improve the flexibility of the polyimides since their T_g values were usually as high as those of polymers made from p-diamines. Only slight differences in mechanical properties of the isomeric polyimide films were attributable to the variations in isomeric structure, except for those properties dependent upon T_g changes, such as elevated temperature mechanical properties. A study of the thermooxidative stability of the polyimides showed little difference between the polymers prepared from the diaminobenzophenones, but marked differences were observed between the individual members of the diaminodiphenylmethane-derived polyimides.     

The effects of monophenol chain terminators on the structure–property relationships of controlled epoxy networks

Five families of new controlled epoxy thermosets (CENs) using three monophenol chain terminators were prepared to study systematic changes in the structure and amount of the monophenol and the initial molecular weight between crosslinks (M_c,i) on the properties of epoxy thermosets. Glass transition temperature (T_g) decreases with monophenol mole fraction (χ) in proportion to both the concentration and flexibility of the chain terminator. Distinct serial relations for T_g depression were observed for the three M_c,i families. Dynamic mechanical analysis (DMA) shows significant perturbations of the relaxation behavior with added terminator as evidenced by decrease in peak tan δ and in post T_g damping. The rubbery coefficients of thermal expansion (CTE) increases with monophenol concentration only at χ > 0.05 and shows distinct curvature versus temperature, but is largely invariant with monophenol flexibility. The thermal stability of terminated CENs decreases only slightly with χ and little difference was found with monophenol structure. Most surprisingly, fracture toughness decreases markedly and discontinuously with χ depending on M_c,i. The values of the critical monophenol concentration at which fracture toughness markedly decreases (χ_c) are inversely proportional to M_c,i but are independent of monophenol flexibility. No correlation of χ_c with any of the calculated network structure parameters was apparent. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1632–1640, 2008     

Polyimide structure–property relationships. I. Polymers from fluorene-derived diamines

A series of fluorene and fluorenone diamines were polymerized with two aromatic dianhydrides, and the resulting polyamic acids were cyclodehydrated to aromatic polyimides. A study of the mechanical properties of the polyimide films disclosed they are among the stiffest reported to date, with an excellent retention of rigidity at elevated temperatures. Comparisons of the tensile properties and glass transition temperatures of the fluorene-derived polymer films with those from the corresponding open-chain polyimide films established that the unusual rigidity, especially at elevated temperatures, was in large part due to the contribution of the bulky, tricyclic fluorene (one) moieties in the polymer structures.     

Effect of solvent on radiation grafting and crosslinking of polyethylene

Crosslinking of polyethylene influences its swelling properties. It could be expected that pre-crosslinking of polyethylene influences the rate and yield of grafting as well. This is demonstrated by pre-crosslinking of polyethylene and by its subsequent grafting with styrene after the trapped radicals had been annealed out.In order to obtain more direct information about the influence of swelling agent on polyethylene crosslinking, the elastic modulus of the crosslinked polyethylene was investigated. Stress–strain curves of polyethylene samples irradiated in different environments were recorded in molten state at 165 °C. The results show that irradiation of swollen polyethylene produces fewer effective crosslinks than does irradiation of dry polymer.     

Remarkably stable amphiphilic random copolymer assemblies: A structure–property relationship study

Synthesis of a library of amphiphilic random copolymers from a single reactive pre‐polymer and their self‐assembly is reported. Post‐polymerization modifications of the parent polymer containing pendant N‐hydroxy succinimide (NHS) ester groups with various oligooxyethylene (OE) amines produce amphiphilic random copolymers with same degree of polymerization and equal extent of randomness. ¹H‐NMR and FT‐IR data indicate quantitative substitution in all cases. The critical aggregation concentration (CAC) for all the polymers is estimated to be in the range of 10^?5 M. Stability of these nano‐aggregates is studied by photoluminescence using time dependent F—rster Resonance Energy Transfer (FRET) between co‐encapsulated lipophilic dyes namely DiO and DiI in the hydrophobic pocket of the aggregates. These studies suggest remarkably high stability for all systems. However those with shorter hydrophilic pendant chains are found to be even more robust. Morphology is examined by high resolution transmission electron microscopy (HRTEM) which reveals multi‐micellar clusters and vesicles for polymers containing short and longer OE segments, respectively. Encapsulation efficacy is tested with both hydrophobic and hydrophilic guest molecules. All of them can encapsulate hydrophobic guest pyrene while a hydrophilic dye Calcein can be sequestered only in vesicle forming polymers. Lower critical solution temperature (LCST) is exhibited by only one polymer that contains the shortest OE chains. All polymers exhibit excellent cell viability as determined by MTT assay. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 4932–4943