X-ray and neutron scattering studies of poly(ester carbonate)/poly(ethylene terephthalate) alloys

Quenched blends of poly(ester carbonate) (PEC) and poly(ethylene terephthalate) (PET) have a single T_g and behave as single-phase amorphous alloys up to 67% PET. However, small-angle neutron scattering (SANS) data show that the PET molecules are not statistically distributed as classical Gaussian coils in the PEC matrix. In quenched amorphous PEC-rich films (a single phase), PET-rich domains of varying PET concentration appear to be randomly distributed in the PEC matrix, and the excess SANS intensity is attributable to fluctuations in PET concentrations. Wide- and small-angle X-ray scattering data and SANS results show incomplete phase separation of PET and PEC molecules upon annealing. A possible model for annealed blends (two phases) might be domains of folded-chain, crystalline PET with interlamellar amorphous regions composed of a mixture of PET and PEC molecules. These domains are dispersed in the amorphous PEC matrix.     

Small angle neutron scattering study of the structure of a triblock copolymer of styrene and isoprene during extension

A triblock copolymer with a styrene weight fraction of 0.41, has been examined at various extension ratios using small angle neutron scattering. The original ‘polycrystalline’ material with a face centred cubic arrangement of styrene domains acquires orientation as the extension ratio increases. Affine deformation is not obeyed at the supramolecular level and there is some evidence for non-uniform stress at this level.     

Properties of the polyethylene/poly (2,6-dimethyl-1,4-phenylene ether)/polystyrene system in the presence of SEPS block copolymers

An immiscible polymer system of polyethylene (HDPE)/poly(2,6-dimethyl-1,4-phenylene ether)/polystyrene was compatibilized in the presence of a specific formulated compatibilizer and the properties of this system were studied, in particular, as a function of the poly(phenylene ether) and polystyrene content in the blend with polyethylene and as a function of compatibilizer concentration. The compatibilizer used was a hydrogenated styrene/isoprene/styrene triblock copolymer (SEPS) which also contained quantities of polypropylene and paraffin oil. Selected thermal, mechanical, and processing properties were investigated and their special features are discussed. In relation to specific properties like the modulus of elasticity and notched Izod impact strength, the polymer system with a hydrogenated SEPS triblock copolymer investigated seems to be a better compatibilized system than other blends described. The phase behavior of the polymer system was characterized using DSC and showed three general polymer phases: a partially crystalline polyethylene phase, an amorphous mixed phase of miscible poly(phenylene ether) and polystyrene, as well as a preferred isotactic crystalline polypropylene phase. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1835–1842, 1997     

Small angle neutron scattering study of the structure and formation of MCM-41 mesoporous molecular sieves

The nanoscale structure and synthesis mechanisms of the MCM-41 class of inorganic mesoporous materials have been investigated by small angle neutron scattering (SANS). SANS measurements with solvents imbibed in the pores to vary the scattering contrast demonstrate that the low angle diffraction peaks from these materials are entirely due to the pore structure and that the pores are fully accessible to both aqueous and organic solvents. Static and shear flow SANS measurements on the concentrated cationic surfactant and silicate precursor solutions typically used in the synthesis of the mesopore materials indicate that the existence of preassembled supramolecular arrays that mimic the final pore structure is not essential for the synthesis of these materials.     

Small angle neutron scattering study of deuterated sodium dodecylsulfate micellization in dilute poly((2-dimethylamino)ethyl methacrylate) solutions

Poly((2-dimethylamino)ethyl methacrylate) with 60,000 g/mol and a narrow polydispersity (1.12) was synthesized using group transfer polymerization in order to investigate the structure of poly((2-dimethylamino)ethyl methacrylate)/sodium dodecylsufate complexes in water. The synthesized polymer chain conformation in water was studied as a function of deuterated sodium dodecylsulfate concentration using small angle neutron scattering. We found three transitions of the poly((2-dimethylamino)ethyl methacrylate) chain conformation induced by the added deuterated sodium dodecylsulfate. The transitions resulted from interactions between the polymer and the surfactant, so that micelles are formed along the polymer backbone above the critical aggregation concentration. The structure of micelles in a poly((2-dimethylamino)ethyl methacrylate)/deuterated sodium dodecylsulfate solution was analyzed through model fitting of the small angle neutron scattering data measured at the condition where the poly((2-dimethylamino)ethyl methacrylate) was contrast-matched with a mixture of 80% H₂O and 20% D₂O.     

Polyaniline and polypyrrole prepared in the presence of surfactants: a comparative conductivity study

Polyaniline and polypyrrole have been prepared by chemical oxidative polymerization of the corresponding monomers in an aqueous medium containing an anionic surfactant—sodium bis(2-ethylhexyl) sulfosuccinate, dodecylbenzenesulfonic acid and its sodium salt, and sodium dodecyl sulfate. Determination of the yield, elemental composition and density proved, and FTIR spectroscopy confirmed, that the anionic surfactants become incorporated in the conducting polymers. The polymerizations in the presence of a cationic surfactant, tetradecyltrimethylammonium bromide, were carried out for comparison. While the conductivity of polypyrrole became enhanced after the introduction of an anionic surfactant, the changes in the conductivity of polyaniline were marginal. The conductivity changes in both polymers during thermal ageing were measured at 175 °C. The electrical stability of polyaniline was better than that of polypyrrole. The presence of a surfactant improved the stability of conductivity of polypyrrole but reduced the electrical stability of polyaniline.     

Time‐resolved small‐angle X‐ray scattering study of void fraction evolution in high‐density polyethylene during stress unloading and strain recovery

By means of time‐resolved small‐angle X‐ray scattering, we developed an analysis methodology to assess the void volume fraction ?_v in high‐density polyethylene (HDPE) during tensile testing. The specimens were first drawn up to different imposed strains, and subsequently were subjected to stress unloading and strain recovery stages. During the loading stage, ?_v progressively increased with the strain level, starting from a well‐defined onset strain prior to the yield point. In particular, ?_v reached a maximum of 8.75 vol% for a strain of 12.5% in the case of a HDPE grade with a molecular weight of 105 000 g mol^?1. Stress unloading and strain recovery caused a decrease in ?_v attained at the end of the loading stage. For a HDPE grade with a molecular weight of 55 000 g mol^?1, ?_v was more important during the loading stage and the decrease in ?_v was less marked during the stress unloading stage when compared to the HDPE with molecular weight of 105 000 g mol^?1. The residual and reversible components of void volume fraction were revealed. © 2015 Society of Chemical Industry     

Effect of processing parameters on the morphology development during extrusion of polyethylene tape: An in-line small-angle X-ray scattering (SAXS) study

The in-line development of crystalline morphology and orientation during melt extrusion of low density polyethylene (LDPE) tape at nil and low haul-off speeds has been investigated using Small-Angle X-Ray Scattering (SAXS). The processing parameters, namely haul-off speed and distance down the tape-line have been varied and the resulting crystalline morphology is described from detailed analysis of the SAXS data. Increasing haul-off speed increased orientation in the polymer tape and the resulting morphology could be described in terms of regular lamellar stacking perpendicular to the elongation direction. In contrast, under nil haul-off conditions the tape still showed some orientation down the tape-line, but a shish-kebab structure prevails. The final lamellae thickness ( ∼50 Å) and bulk crystallinity (∼20%), were low at, for all processing conditions investigated, which is attributed to the significant short-chain branching in the polymer acting as point defects limiting lamellae crystal growth.     

Incoherent neutron scattering study on the local dynamics in polystyrene and poly(vinyl methyl ether) blends

Neutron scattering study using the fixed elastic window technique is performed to investigate the effect of blending on the local dynamics of each component for polystyrene and poly(vinyl methyl ether) blends. The non-Gaussian scattering behavior observed above a certain temperature for the PVME component can be well explained by considering the rotational motions of methyl groups around O-CH₃ axis. The mean-square displacements of the vibrational motions were approximately proportional to absolute temperature below the glass transition temperature, which is a signature of harmonic oscillations, and were hardly affected by blending PS. On the other hand, the mean-square displacement of the PS component in the blend was almost the same as that of pure PS, while the non-Gaussian parameter for the former was much larger in comparison with that of the latter. Blending with PVME leads to a large increase in the dynamical heterogeneity for the PS component.     

Characterization of compositional heterogeneity in the polyethylene prepared with bis(imino)pyridyl iron(II) precatalyst and triethylaluminum

Analytical tools including solvent gradient elution fractionation (SGEF), GPC, ¹³C NMR, and differential scanning calorimetry (DSC) are integrated for the characterization of compositional heterogeneity in the polyethylene (PE) prepared with the LFeCl₂/AlEt₃ catalytic system. The results indicate that at least two different kinds of catalytic species are present in ethylene polymerization. One active species generating branched PE gives low molecular weight; another kind of active species gives high molecular weight PE with high linear structure. The amount of branch decreases with increasing the molecular weights, and the small proportion of the branched PE shows low molecular weight with vinyl‐terminated end group, indicating that the branched PE is generated from the catalytic species giving low activity. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis of branched polyethylene by ethylene homopolymerization with a novel (α‐diimine)nickel complex in the presence of methylaluminoxane

Branched polyethylene (PE) was prepared with a novel (α‐diimine)nickel(II) complex of 2,3‐bis(2,6‐dimethylphenyl)‐butanediimine nickel dichloride {[2,6‐(CH₃)₂C₆H₃? N?C(CH₃)C(CH₃)?N? 2,6‐(CH₃)₂C₆H₃]NiCl₂} activated by methylaluminoxane in the presence of a single ethylene monomer. The influences of various polymerization conditions, including the temperature, Al/Ni molar ratio, Ni catalyst concentration, and time, on the catalytic activity, molecular weight, degree of branching, and branch length of PE were investigated. According to gel permeation chromatography, the weight‐average molecular weights of the polymers obtained ranged from 1.7 × 10⁵ to 6.0 × 10⁵, with narrow molecular weight distributions of 2.0–3.5. The degree of branching in the polymers rapidly increased with the polymerization temperature increasing; this led to highly crystalline to totally amorphous polymers, but it was independent of the Al/Ni molar ratio and catalyst concentration. At polymerization temperatures greater than 20°C, the resultant PE was confirmed by ¹³C‐NMR to contain significant amounts of not only methyl but also ethyl, propyl, butyl, amyl, and long branches (longer than six carbons). The formation of the branches could be illustrated by the chain walking mechanism, which controlled their specific spacing and conformational arrangements with one another. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1123–1132, 2002; DOI 10.1002/app.10398     

The role of the ratio (PEG:PPG) of a triblock copolymer (PPG‐b‐PEG‐b‐PPG) in the cure kinetics,miscibility and thermal and mechanical properties in an epoxy matrix

The aim of this study was to evaluate the role of different poly(ethylene glycol):poly(propylene glycol) (PEG:PPG) molar ratios in a triblock copolymer in the cure kinetics, miscibility and thermal and mechanical properties in an epoxy matrix. The poly(propylene glycol)‐block‐poly(ethylene glycol)‐block‐poly(propylene glycol) (PPG‐b‐PEG‐b‐PPG) triblock copolymers used had two different molecular masses: 3300 and 2000 g mol^?1. The mass concentration of PEG in the copolymer structure played a key role in the miscibility and cure kinetics of the blend as well as in the thermal–mechanical properties. Phase separation was observed only for blends formed with the 3300 g mol^?1 triblock copolymer at 20 wt%. Concerning thermal properties, the miscibility of the copolymer in the epoxy matrix reduced the T_g value by 13 °C, although a 62% increase in fracture toughness (K_IC) was observed. After the addition of PPG‐b‐PEG‐b‐PPG with 3300 g mol^?1 there was a reduction in the modulus of elasticity by 8% compared to the neat matrix; no significant changes were observed in T_g values for the immiscible system. The use of PPG‐b‐PEG‐b‐PPG with 2000 g mol^?1 reduced the modulus of elasticity by approximately 47% and increased toughness (K_IC) up to 43%. Finally, for the curing kinetics of all materials, the incorporation of the triblock copolymer PPG‐b‐PEG‐b‐PPG delayed the cure reaction of the DGEBA/DDM (DGEBA, diglycidyl ether of bisphenol A; DDM, Q3‐4,4′‐Diaminodiphenylmethane) system when there is miscibility and accelerated the cure reaction when it is immiscible. All experimental curing reactions could be fitted to the Kamal autocatalytic model presenting an excellent agreement with experimental data. This model was able to capture some interesting features of the addition of triblock copolymers in an epoxy resin. © 2018 Society of Chemical Industry     

Time resolved study of shear-induced crystallization of poly(p-dioxanone) polymers under low-shear, nucleation-enhancing shear conditions by small angle light scattering and optical microscopy

Isothermal crystallization of the biodegradable homopolymer polyester poly(p-dioxanone) (PDS), and the p-dioxanone copolymer with glycolide PDS-copolymer were studied in situ and in real-time under quiescent or nucleation-enhancing shear conditions. It was found that the spherulitic growth rates remain unchanged with shear, while the nucleation density increases dramatically. Nucleation-enhancing shear conditions, which do not alter the general spherulitic morphology, consist of a short-duration step-shear. This is in contrast to isothermal crystallization under steady-shear conditions, where at low-shear rates, fibrillar crystalline structures form. At high crystallization temperatures, where under quiescent conditions crystal development requires several days, both PDS, and the PDS-copolymer can be made to crystallize in several hours by the imposition of a step-shear.     

Synthesis of di(4‐hydroxyl benzophenone) sebacate and its usage as initiator in the photocrosslinking of polyethylene

A new benzophenone (BP) derivative with a long carbon chain and two chromophoric groups—di (4‐hydroxyl benzophenone) sebacate (BP‐S) used as a photoinitiator in the photocrosslinking of polyethylene (PE) has been synthesized and characterized by ultraviolet (UV) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and elemental analysis. The kinetic characteristics of BP‐S photoinitiated crosslinking of PE in the melt and its compatibility with PE resin have been examined by gel content measurement and thermal migration experiment. The results show that BP‐S is an excellent photoinitiator, which has better compatibility, less volatility, higher photoinitiating efficiency, and longer storage time than BP itself. It is promising for industrial applications of the photocrosslinking of polyolefins. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1581–1586, 2002;     

Aggregation behaviour of stereoregular poly(methyl methacrylates) in dilute solution: light scattering and proton n.m.r. study

The aggregation behaviour of syndiotactic and isotactic poly(methyl methacrylate) in methyl ethyl ketone, n-butyl acetate, and 2-ethoxyethanol was investigated by light scattering and ¹H n.m.r. spectroscopy. Syndiotactic poly(methyl methacrylate) remains in its molecular form in solution at temperatures above 60°–70°C; on cooling it undergoes aggregation followed by macroscopic separation (precipitation) of the polymer from solution. The rate of these processes depends on temperature, concentration of the polymer, and solvent. Molecular solutions of isotactic poly(methyl methacrylate) can be prepared only by long-term heating at temperatures above 100°–130°C. During cooling, isotactic macromolecules prior to separation form stable associates in the region limited by discrete temperatures, and below this region polymer precipitates. The individual stereo forms of poly(methyl methacrylate) are separated from solution at different temperatures which are above the θ-temperatures of the atactic polymer.     

Physical ageing and the embrittlement of poly(hydroxybutyrate) on storage: a time resolved small angle X-ray scattering study

Time resolved small angle X-ray scattering is used to probe the microstructural changes occurring in a sample of poly(hydroxybutyrate), aged at room temperature, during a heating cycle designed to reverse any physical ageing. Evidence for the reversal of physical ageing is seen, but is unlikely to account for all the changes in mechanical properties in this polymer on storage at room temperature. © 1998 SCI.     

A Fourier transform infra-red study of the phase behaviour of polymer blends. Ethylene-vinyl acetate copolymer blends with poly(vinyl chloride) and chlorinated polyethylene

Fourier transform infra-red studies of ethylene-vinyl acetate (EVA) blends with poly(vinyl chloride) (PVC) and chlorinated polyethylene (CPE) are presented. Previous studies have demonstrated that these blends are compatible at ambient temperature and exhibit lower critical solution temperatures (LCST) in a range that is readily accessible and below the onset of significant polymer degradation. Infra-red spectra of EVA-PVC and EVA-CPE films cast from solution and recorded at room temperature exhibit the familiar frequency shifts and band broadenings of the carbonyl stretching vibration that are consistent with compatible blend systems. Significantly, at temperatures above the LCST, these spectral features are not observed, which implies phase separation. By monitoring the frequency of the EVA carbonyl stretching vibration in samples of the blends, an estimation of the relative strength of the intermolecular interactions has been obtained as a function of temperature. A non-linear relationship is observed and the temperature at which the relative strength of the intermolecular interaction appears very weak correlates with the LCST. The implications of these results are discussed.     

Electrical conductivity of LTA‐zeolite in the presence of poly(vinyl alcohol) and poly(vinyl pyrrolidone) polymers

In this work we studied the electrical behavior of Linde type A zeolite (K⁺) in the presence of two polymers, poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP), with excellent film forming properties. Homogeneous composite thin films of PVA/LTA‐zeolite and PVP/LTA‐zeolite were prepared with different zeolite concentrations. The current?voltage (I?V) characteristics of the composites were measured at different applied voltages. The results show that the conductivity properties are composition‐ratio‐dependent and are also related to the type of polymers. Moreover, a well‐defined step‐like change was detected in the I?V curve of PVP/LTA‐zeolite at very high applied voltage. © 2013 Society of Chemical Industry     

Synthesis and characterization of poly(methylene disulfide) and poly(ethylene disulfide) polymers in the presence of a phase transfer catalyst

Poly(methylene disulfide) and poly(ethylene disulfide) were synthesized from the polycondensation of methylene dichloride and ethylene dichloride monomers, respectively, in the presence of benzyltriethylammonium chloride as a phase transfer catalyst. The structures of the synthesized polysulfides were confirmed via the elemental analysis, attenuated total reflectance Fourier transform infrared spectroscopy and X-ray diffraction techniques. Moreover, the thermal behaviors of synthesized poly(methylene disulfide) and poly(ethylene disulfide) were characterized using differential scanning calorimetry and thermogravimetric analysis methods. The synthesized poly(methylene disulfide) and poly(ethylene disulfide) have molecular weights of about 2262 and 2863 g/mol, respectively. In addition, the polymers have crystalline structures absorbed in the amorphous sections. However, the d-spacing of polymers’ crystalline parts was different. Moreover, poly(methylene disulfide) and poly(ethylene disulfide) have a two- and one-step degradation behavior, respectively.     

Synthesis and characterization of the feed ratio of polyethylene oxide (0 ∼ 10 wt % PEO) in the nylon‐6/PEO copolymer system

In this work, we have synthesis nylon‐6/polyethylene oxide (PEO) copolymer system based on feed ratio of PEO (0～ 10 wt %) through condensation polymerization in a pilot scale. The structure of copolymer was confirmed by Fourier transform infrared (FTIR) spectroscopy and verified by ¹H nuclear magnetic resonance (¹HNMR). The thermal properties were investigated by differential scanning calorimetry (DSC) and indicated both melting temperature (T_m) and cold crystallization temperature (T_c) appearing unapparent decreased while increased PEO content in copolymers. The incorporation of PEO into the nylon‐6 chain reduced its tensile strength, modulus, and heat distortion temperature (HDT). The notched Izod impact strength of and ductility of the copolymers improved significantly as the PEO content was increased. The plasticizing effect was caused by the soft segments from PEO, which increases the mobility of the molecular chain in the copolymers. The results of mechanical tests agree closely with dynamic mechanical analysis (DMA) measurements. A rheological investigation revealed that neat nylon‐6 and its copolymer displayed similar behavior. The crystalline structure was examined by wide‐angle X‐ray diffraction (WAXD). The results demonstrate that the addition of a little PEO altered the crystallization from the α form to the γ form, mainly owing to the breaking parts of the original H‐bonds by the incorporation of ether groups. A mechanism of interaction between the amide and the ether group in nylon‐6/PEO copolymers is proposed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011