Small-angle Laser Light Scattering Research Articles

Promoted liquid-liquid phase separation of PEO/PS blends with very low LiTFSI fraction

Studies on phase behavior of polymer blends with lithium salts can provide a theoretical basis for developing solid polymer electrolytes in lithium-ion battery. In this paper, the liquid-liquid phase separation of PEO/PS/LiTFSI system is characterized by small angle neutron scattering (SANS) and small angle laser light scattering (SALLS). A combination of the Debye-Bueche equation and Ornstein-Zernike scattering function is employed to fit the SANS data in the homogeneous state. The thermodynamic parameters, including the forward scattering intensity I0, correlation length ξ, spinodal temperature Ts, effective interaction parameter χeff and cloud point boundaries, are obtained. The cloud point temperatures increase with LiTFSI concentration, especially at the low PEO fractions. We conclude that even a small amount of lithium salt enhances the liquid-liquid phase separation of PEO/PS blends significantly, and the effect of electrostatic interaction increases with temperature.

Synthesis and characterization of a renewable cyanate ester/polycarbonate network derived from eugenol

A homogenous polycarbonate/cyanate ester network has been prepared from a renewable, eugenol-derived bisphenol. The pure polycarbonate exhibited a Tg of 71 °C, Mn = 8360, and polydispersity of 1.88. An 80:20 blend of cyanate ester: polycarbonate was prepared and thermally cured. The presence of the polycarbonate had no significant effect on the cure behavior of the cyanate ester. Small Angle Laser Light Scattering (SALLS) and DSC were used to analyze the blend and no phase separation was observed either during or after cure, suggesting that a homogenous network was generated. TMA of the resulting composite material revealed a single Tg of 132 °C (tan δ), roughly 55 °C lower than the Tg of the pure polycyanurate and 60 °C higher than the polycarbonate. A solvent extraction study showed that the polycarbonate could be quantitatively separated from the thermoset matrix after cure. This result proved that no chemical grafting occured under the cure conditions employed. The excellent miscibility of the polycarbonate and cyanate ester coupled with the efficient cure of the blend to a homogenous network suggests that these types of blends may have applications for fabrication of toughened composite structures.

Influence of shear force on floc properties and residual aluminum in humic acid treatment by nano-Al13

The impacts of various shear forces on floc sizes and structures in humic acid coagulations by polyaluminum chloride (PACl) and nano-Al13 were comparatively studied in this paper. The dynamic floc size was monitored by use of a laser diffraction particle sizing device. The floc structure was evaluated in terms of fractal dimension, analyzed by small-angle laser light scattering (SALLS). The effect of increased shear rate on residual Al of the coagulation effluents was then analyzed on the basis of different floc characteristics generated under various shear conditions. The results showed that floc size decreased with the increasing shear rate for both Al13 and PACl. Besides, floc strength and re-formation ability were also weakened by the enhanced shear force. Al13 resulted in small, strong and better recoverable flocs than PACl and moreover, in the shear range of 100–300 revolution per minute (rpm) (G=40.7–178.3s−1), the characteristics of HA-Al13 flocs displayed smaller scale changes than those of HA-PACl flocs. The results of residual Al measurements proved that with shear increased, the residual Al increased continuously but Al13 presented less sensitivity to the varying shear forces. PACl contributed higher residual Al than Al13 under the same shear condition.

Coagulation behaviors and in-situ flocs characteristics of composite coagulants in cyanide-containing wastewater: Role of cationic polyelectrolyte

In this paper, composite coagulants (PFS, PFSC05, PFSC1 and PFSC5), prepared by mixing polyferric sulfate (PFS) and cationic polyelectrolyte (CP) coagulants with different weight percent (W p) of CP (W p = 0%, 0.5%, 1% and 5%, respectively), were adopted to treat cyanide-containing wastewater. PFSC5 exhibited superior coagulation performances at optimal conditions: the removal of total cyanide (TCN) and chemical oxygen demand (COD) was 95%–97% and 50%–55%, respectively. The effects of CP on the properties and structure of flocs were investigated by laser diffraction instrument and small-angle laser light scattering (SALLS), respectively. The results show that the flocs of PFSC5 have higher growth rate, higher strength factor and lower recovery factor than other flocs. They are also much denser and more uniform owing to the higher fractal dimension (Df) and less microflocs (10–100 μm). Furthermore, the dense structure of the PFSC5 flocs can be restored after shear and is more resistant to hydraulic conditions. Particularly, detailed morphology evolution of the flocs was in-situ detected by on-line particle imaging. Due to strong ionic strength in wastewater, the CP in PFSC5 plays a significant role of adsorption, while the main mechanism of CP is electrostatic patch aggregation during the PFSC05 systems.

In-situ Cure and Cure Kinetic Analysis of a Liquid Rubber Modified Epoxy Resin

The in-situ cure and cure kinetics of an epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) polymerized with an anhydride hardener and its mixtures with a liquid polybutadiene rubber having hydroxyl functionality (HTPB) were studied using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC) in an isothermal mode. The cure reaction was monitored in-situ by FTIR spectroscopy by observing variation in intensity of epoxy, anhydride, and ester bands. The cure reaction mechanisms by which the network structure of epoxy was developed were discussed. Isothermal mode DSC measurements were performed at selected temperatures. The reaction followed an autocatalytic mechanism, and kinetic analysis was done by a phenomenological model developed by Kamal. Good fits were obtained between the autocatalytic model and the experimental data up to the vitrification state. Afterward, the reaction became diffusion controlled. The reaction during the later stages of cure was explained by introducing a diffusion factor, which agreed well with the kinetic data. The nature of the developing morphology of modified epoxies was analyzed by optical microscopy (OM) and small angle laser light scattering (SALLS) technique. The ultimate morphology of the cured blends was analyzed using scanning electron microscopy (SEM). The cure kinetics has been correlated with the developed morphology to get insight into the mechanism of reaction-induced microphase separation.

Viscoelastic effects in thermoplastic poly(styrene-acrylonitrile)-modified epoxy–DDM system during reaction induced phase separation

The viscoelastic phase separation of a poly(styrene-co-acrylonitrile) (SAN) modified epoxy system based on the diglycidyl ether of bisphenol A (DGEBA) cured with 4,4′-diaminodiphenylmethane (DDM) has been monitored in situ using rheometry, optical microscopy (OM) and small angle laser light scattering (SALLS). The amount of SAN in the epoxy blends were 3.6, 6.9, 10, and 12.9 wt%. The relationship between rheological properties and phase separation was carefully explored. The evolution of storage modulus, loss modulus, and tan δ were found to be closely related to the evolution of complex phase separation. From the rheological profile, two gel points are identified, corresponding to physical gelation and chemical gelation, the first one because of viscoelastic phase separation and the second one related to crosslinking of the epoxy resin, these depend on the cure temperature and amount of thermoplastic. Further SALLS investigations investigated the mechanism of phase separation. The time-dependent peak scattering vector was simulated with a Maxwell-type viscoelastic relaxation equation. Relaxation times obtained at different temperatures for the blends could be described by the Williams–Landel–Ferry equation. Moreover, the development of light scattering profile follows the Tanaka model of viscoelastic phase separation.

Novel ferromagnetic nanoparticle composited PACls and their coagulation characteristics

Effects of magnetic nanoparticles on inorganic coagulants and their coagulation performances were studied in the present work. The Fe 3O 4–SiO 2 core-shell particle (FSCSP) and superfine iron (SI), were compounded with polyaluminium chloride of basicity 2.0 (PACl2.0), providing magnetic PACl2.0s (MPACl2.0s). The physiochemical properties of ferromagnetic nanoparticles were investigated using transmission electron microscopy (TEM), the BET method and a zeta potentiometric analyzer. The Al species distributions of the MPACl2.0s and PACl2.0 were examined by liquid 27Al NMR. Jar tests were employed to evaluate the coagulation performances. Floc properties were assessed by use of the electromotive microscope (EM) and small angle laser light scattering (SALLS). The results showed that modified layers of nanoparticles mitigated agglomeration. FSCSP had a larger specific area and pore volume than SI. The addition of ferromagnetic nanoparticles obviously increased the content of Al un. MPACl2.0s performed better than PACl2.0 in turbidity removal and DOC removal when dosed less than 0.06 mmol/L as Al. Generally, PACl2.0 + FSCSP (50 mg/L) performed best. Large, loose and weak flocs were produced by MPACl2.0s, which were preferred for the magnetic powder recycling. A plausible structure, Al species-nanoparticles cluster, contributing to the unique properties of MPACl2.0 flocs, was proposed.

制备方法对聚合物共混物相分离与黏弹弛豫的影响

The liquid-liquid phase-separation(LLPS) and rheological behavior of isotactic polypropylene/ethylene-propylene rubber(iPP/EPR) blends prepared through different methods were studied through small angle laser light scattering(SALLS) and dynamic rheological measurement.The calculated apparent diffusion coefficient(Dapp) during early stage of LLPS and the time required by the same qmax shifting during late stage of LLPS were investigated.It is found that the phase separation rate of melt-blended iPP/EPR(m-iPP/EPR) is higher than that of the solution-blended samples(s-iPP/EPR).Moreover,the results obtained through the dynamic rheological tests indicate that the relaxation rate of m-iPP/EPR sample is faster than that of s-iPP/EPR.It is suggested that the different phase separation rates between m-iPP/EPR and s-iPP/EPR are ascribed to the motion ability of polymer chain.

SYNTHESIS AND CHARACTERIZATION OF POLYIMIDE WITH ARYLENE SULFIDE STRUCTURE

A polyimide with arylene sulphide structure units was synthesized via polycondensation of 4,4′- diamino diphenyl sulphide (SDA) and pyromellitic dianhydrid (PMDA) followed by thermal imidization and chemical imidization. A real-time online tracing method was built up by using the advanced rheology expanded systems (ARES) to monitor the polycondensation,and the effects of reaction conditions on the thermal and chemical imidization were studied by thermogravimetic analysis. The structures and properties of the polyimide were characterized by fourier transform infrared spectroscopy ( FTIR ),small angle laser light scattering (SALS),contact angle analysis and differential scanning calorimetry (DSC) etc. Results show that the surface properties of polyimide films are great improved by introducing the arylene sulphide structure into the main chain of polyimide,and the adhesion work between the new polyimide and copper foil is higher than the traditional one. The weight-average molecular weight of the polyimide is (6. 7 ± 1. 6) × 104; the decomposition temperature is higher than 560℃ ; DSC results show that the polyimides prepared by both thermal and chemical imidization have high glass transition temperature,and in comparison,chemical imidization gives rise to a higher degree of imidization and a higher glass transition temperature.

Dynamics of Phase Separation in Poly(acrylonitrile-butadiene-styrene)-Modified Epoxy/DDS System: Kinetics and Viscoelastic Effects

The dynamics of phase separation and final morphologies of poly(acrylonitrile-butadiene-styrene) (ABS)-modified epoxy system based on diglycidyl ether of bisphenol A (DGEBA) cured with 4,4'-diaminodiphenylsulfone (DDS) have been monitored in situ throughout the entire curing process by using optical microscopy (OM), differential scanning calorimetry (DSC), rheometry, and small-angle laser light scattering (SALLS). The evolution of phase separation and final morphologies with substructures were explored by OM. The final morphologies of the blend cured at 150 and 165 °C are of phase-inverted type and are quite different from the final morphologies of the same blend cured at 180 °C, in which the final morphologies are cocontinuous. AFM observations of the fully cured sample confirmed the existence of three different phases, the epoxy continuous phase, SAN (styrene/acrylonitrile) continuous phase, and PB droplets at the interface, with a strong tendency to stay at SAN continuous phase. Furthermore, the continuous epoxy phase contains SAN particles and the continuous SAN phase contains epoxy particles. Cure kinetics and rheological results correspond well with the viscoelastic phase separation revealed by OM. The SALLS results display clearly that the phase separation takes place according to nucleation and growth mechanism followed by spinodal decomposition. The development of light scattering patterns during the second stage phase separation follows the Cahn-Hilliard model of spinodal demixing. Furthermore, the evolution of the scattering vector follows a Maxwell-type relaxation equation establishing the viscoelastic behavior of phase separation. The relaxation time of phase separation can be described by the Williams-Landel-Ferry equation for viscoelasticity. As a whole, the dependence of phase separation on cure temperature and the development of final morphologies and the associated mechanisms were explored in detail for the complex epoxy/ABS system.

Influence of floc structure on coagulation–microfiltration performance: Effect of Al speciation characteristics of PACls

Microfiltration performance in coagulation–microfiltration hybrid systems (without settling process) has strong correlation with the floc structure. This study investigated the effect of Al speciation distribution (Al a, Al b and Al c) of PACls (polyaluminum chlorides) on floc structure and the overall membrane performance. The floc properties, analyzed with small angle laser light scattering (SALLS), of different aluminum based coagulants, AlCl 3 (PACla, with high Al a species), polyaluminum chloride (PAClb, with high Al b species), commercial polyaluminum chloride product (PAClp, with similar amount of each Al species) were compared using synthetic waters with added humic acid and kaolin particles. The coagulated waters were then fed through a dead-end microfiltration system using an unstirred batch cell with 0.22 μm PVDF flat sheet membrane. The results show that the property of flocs, largely depended on aluminum species, is the most influencing factor for membrane filtration behaviors. The floc sizes from different coagulants are in the following order PACla > PAClp > PAClb, which is consistent with the amount of Al a species in the PACls. The fractal dimension values are very similar for each PACls. The floc strength follows the order of PACla > PAClb > PAClp. Cake made of PACla-flocs shows a noticeable flux advantage followed by PAClp-flocs and PAClb-flocs, which agrees well with the order of floc size. However, the flux decline of PAClp-flocs is much worse than PACla-flocs although both of them have similar final steady-state floc size. The difference between the flux of PAClb-flocs and PAClp-flocs is not as significant as the difference between their floc sizes. This can be explained that the PAClp-flocs are much more fragile than PAClb-floc due to its weak floc strength. These results also suggest that floc strength is another very important factor influencing the filtration performance.

Complex Phase Separation in Poly(acrylonitrile−butadiene−styrene)-Modified Epoxy/4,4′-Diaminodiphenyl Sulfone Blends: Generation of New Micro- and Nanosubstructures

The epoxy system containing diglycidyl ether of bisphenol A and 4,4'-diaminodiphenyl sulfone is modified with poly(acrylonitrile-butadiene-styrene) (ABS) to explore the effects of the ABS content on the phase morphology, mechanism of phase separation, and viscoelastic properties. The amount of ABS in the blends was 5, 10, 15, and 20 parts per hundred of epoxy resin (phr). Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) were employed to investigate the final morphology of ABS-modified epoxy blends. Scanning electron microscopic studies of 15 phr ABS-modified epoxy blends reveal a bicontinuous structure in which both epoxy and ABS are continuous, with substructures of the ABS phase dispersed in the continuous epoxy phase and substructures of the epoxy phase dispersed in the continuous ABS phase. TEM micrographs of 15 phr ABS-modified epoxy blends confirm the results observed by SEM. TEM micrographs reveal the existence of nanosubstructures of ABS in 20 phr ABS-modified epoxy blends. To the best of our knowledge, to date, nanosubstructures have never been reported in any epoxy/thermoplastic blends. The influence of the concentration of the thermoplastic on the generated morphology as analyzed by SEM and TEM was explained in detail. The evolution and mechanism of phase separation was investigated in detail by optical microscopy (OM) and small-angle laser light scattering (SALLS). At concentrations lower than 10 phr the system phase separates through nucleation and growth (NG). However, at higher concentrations, 15 and 20 phr, the blends phase separate through both NG and spinodal decomposition mechanisms. On the basis of OM and SALLS, we conclude that the phenomenon of complex substructure formation in dynamic asymmetric blends is due to the combined effect of hydrodynamics and viscoelasticity. Additionally, dynamic mechanical analysis was carried out to evaluate the viscoelastic behavior of the cross-linked epoxy/ABS blends. Finally, apparent weight fractions of epoxy and ABS components in epoxy- and ABS-rich phases were evaluated from T(g) analysis.

Comparison of coagulation behavior and floc structure characteristic of different polyferric-cationic polymer dual-coagulants in humic acid solution

Three polyferric-cationic polymer dual-coagulants were comparatively evaluated in terms of coagulation behavior and floc structure characteristic in the coagulation of humic acid (HA) solution. The first dual-coagulant, PFC–PDADMAC, was prepared by premixing of polyferric chloride (PFC) and polydiallyldimethylammonium (PDADMAC) before dosing. The other two were achieved by dosing PFC and PDADMAC in different order. For the given neutral condition, all three dual-coagulants gave similar HA removal before reaching optimal dosage. The strongest charge neutralization and narrowest effective coagulation dosage range were obtained when PFC was dosed firstly. While the weakest charge neutralization and the broadest effective coagulation dosage were obtained when PDADMAC was used as the primary coagulant. The HA removal of all three dual-coagulants was slightly pH dependent for optimum coagulant doses. Fe(III) hydrolysis species distributions of the dual-coagulants in coagulation process were measured by ferron method. PFC–PDADMAC gave the highest content of active Fe(III) coagulating species which is responsible for the coagulation performance of ferric coagulant. The evolution of floc size and floc fractal dimension ( D f) in coagulation process was measured under optimum dose and neutral condition by laser diffraction instrument and small-angle laser light scattering (SALLS), respectively. All three dual-coagulants gave similar final floc size but different floc growth rate and floc structure. Both the growth rate and D f were in the same order: PFC dosed firstly > PDADMAC dosed firstly > PFC–PDADMAC.

Investigation on LCST behavior of a new amorphous/crystalline polymer blend: Poly(n‐methyl methacrylimide)/poly(vinylidene fluoride)

AbstractThe liquid–liquid phase‐separation (LLPS) behavior of poly(n‐methyl methacrylimide)/poly(vinylidene fluoride) (PMMI/PVDF) blend was studied by using small‐angle laser light scattering (SALLS) and phase contrast microscopy (PCM). The cloud point (Tc) of PMMI/PVDF blend was obtained using SALLS at the heating rate of 1 °C min−1 and it was found that PMMI/PVDF exhibited a low critical solution temperature (LCST) behavior similar to that of PMMA/PVDF. Moreover, Tc of PMMI/PVDF is higher than its melting temperature (Tm) and a large temperature gap between Tc and Tm exists. At the early phase‐separation stage, the apparent diffusion coefficient (Dapp) and the product (2Mk) of the molecules mobility coefficient (M) and the energy gradient coefficient (k) arising from contributions of composition gradient to the energy for PMMI/PVDF (50/50 wt) blend were calculated on the basis of linearized Cahn‐Hilliard‐Cook theory. The kinetic results showed that LLPS of PMMI/PVDF blends followed the spinodal decomposition (SD) mechanism. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1923–1931, 2008

Characterisation of the thickness of transition layer and its relation to mechanical properties of polypropylene/poly(ethylene-co-octene) blends

Poly(ethylene-co-octene) (POE) was mixed into polypropylene (PP) by an internal mixer, which was installed on on-line small-angle laser light scattering (SALLS) device. A new parameter called the thickness (d) of transition layer was introduced to describe the compatibility of PP/POE blends in both dynamic and static states. Using the correlation distance, ac (it was indicative of the dimension of the dispersed phase pellets), d was calculated for the PP/POE blends based on the SALLS theory. The results indicated that the average values of d increased with increasing concentration of dispersed phase and had a maximum value at 40/60(PP/POE) for the blends. And the values of d showed much more violent fluctuation and were much larger at the early stage of mixing, but at a later stage d leveled off and approached to steady state. In addition, the relationships between the thickness of transition layer and mechanical properties were studied. It showed that the notched Izod impact strength and the average values of d of PP/POE blends increased with increasing of POE concentration, while the Young's modulus and flexural modulus decreased. The results indicated that SALLS method was an effective method to deal with diffuse transition layer of PP/POE blends and d was indeed a valid parameter to describe compatibility.

Effect of Shear on Phase-Separation in Polystyrene/Poly(vinyl methyl ether)/Organoclay Nanocomposites

Blends of polystyrene (PS)/poly(vinyl methyl ether) (PVME) modified with two types of organoclay were prepared by solution casting from toluene. The effect of clay addition on the phase separating morphology of PS/PVME blend with critical composition (25/75) was examined both under quiescent conditions and under shear flow. The variation in critical temperature of phase separation was assessed by rheology, small angle laser light scattering (SALLS) and by on-line laser light transmission during shearing at fixed shear rate during heating. Transmission electron microscopy and X-ray diffraction analyses were used to examine the state of delamination and distribution of clay nanoparticles with the blend matrix.

STUDY ON LIQUID-LIQUID PHASE-SEPARATION AND ITS EFFECT ON THE CRYSTALLIZATION KINETICS OF BLENDS COMPOSED OF ISOTACTIC POLYPROPYLENE/ETHYLENE-PROPYLENE RUBBER

The liquid-liquid phase-separation (LLPS) and isothermal crystallization behavior of isotactic polypropylene / ethylene-propylene rubber blend (iPP/EPR) were investigated by using small angle laser light scattering (SALLS),differential scanning calorimetry (DSC),phase contrast microscopy (PCM) and polarized optical microscopy (POM).Results reveal that LLPS of (50/50,W/W) iPP/EPR blend happens at temperatures above the melting point of iPP,and its kinetics follows the spinodal decomposition (SD) mechanism.The apparent diffusion coefficient (D_ app ) and the spinodal temperature (T_s) of the iPP/EPR samples were calculated on the basis of the Cahn-Hilliard theory.Moreover,it is found that the D_ app increases with the increase of temperature,representing the LCST behavior of iPP/EPR.The development of phase morphologies could be obtained by quenching in liquid N_2 the iPP/EPR samples subjected to annealing with different time at 200℃.On the other hand,the structure of iPP/EPR melt appears nearly homogenous at the beginning of LLPS.Furthermore,the co-continuous phases form,and the phase connectivity grows until macroscopic spherical texture generates.Both the increases of phase separation time (t_ ps ) and phase separation temperature (T_ ps ) result in the decrease of the crystallization rate.The kinetic results indicate that the Avrami model is qualified for describing the isothermal crystallization of iPP/EPR.It is believed that the degree of phase-separation has little effect on the crystallization kinetics and the crystallization gives priority to instantaneous nucleation and three-dimension-growth.

PREPARATION OF MICROPOROUS ULTRA HIGH MOLECULAR WEIGHT POLYETHYLENE (UHMWPE) BY THERMALLY INDUCED PHASE SEPARATION OF A UHMWPE/LIQUID PARAFFIN MIXTURE

Ultra-high molecular weight polyethylene (UHMWPE) with a microporous structure was prepared via thermally induced phase separation (TIPS). Liquid paraffin (LP) was used as a diluent in the preparation of microporous UHMWPE. Small angle laser light scattering (SALLS) and differential scanning calorimetry (DSC) were used to determine the phase separation temperatures, i.e . the cloud points and the dynamic crystallization temperatures, respectively. It was found that the cloud points were coincident with the crystallization temperatures, indicating that a solid-liquid phase separation occurred during thermal quenching of the UHMWPE/LP solution, while, no liquid-liquid phase separation above the crystallization temperature was observed. The effects of the content and the molecular weight of UHMWPE on the morphology and average pore size were investigated with field emission scanning electron microscopy (FE-SEM) and mercury porosimetry. With the increase of the content of UHMWPE, the average pore size of the microporous material decreased and the molecular weight of UHMWPE could also influence the pore size slightly.

Effect of blending high‐pressure low‐density polyethylene on the crystallization kinetics of linear low‐density polyethylene

AbstractIt is well known that the addition of a small amount of high‐pressure low‐density polyethylene (HP‐LDPE) to linear low‐density polyethylene (LLDPE) can improve the optical properties of LLDPE, and LLDPE/HP‐LDPE blend is widely applied to various uses in the field of film. The optical haziness of polyethylene blown films, as a result of surface irregularities, is thought to be as a consequence of the different crystallization mechanisms. However, not much effort has been directed toward understanding the effect of HP‐LDPE blending on the overall crystallization kinetics (k) of LLDPE including nucleation rate (n) and crystal lateral growth rate (v). In this study, we investigated the effect of blending 20% HP‐LDPE on the crystallization kinetics of LLDPE polymerized by Ziegler‐Natta catalyst with comonomer of 1‐butene. Furthermore, by combining depolarized light intensity measurement (DLIM) and small‐angle laser light scattering (SALLS), we have established a methodology to estimate the lateral growth rate at lower crystallization temperatures, in which direct measurement of lateral growth by polarized optical microscopy (POM) is impossible due to the formation of extremely small spherulites. This investigation revealed that HP‐LDPE blending leads to enhanced nucleation rate, reduced crystal lateral growth rate, and a slight increase in the overall crystallization kinetics of pure LLDPE. From the estimated crystal lateral growth rate, it was found that the suppression in v from HP‐LDPE blending is larger at lower temperatures than at higher temperatures. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Phase separation in PS/PVME thin and thick films

Phase separation in both thin and thick films of polystyrene (PS) and poly(vinyl methyl ether) (PVME) was studied by small-angle laser light scattering (SALLS), atomic force microscopy (AFM), optical microscopy, and X-ray photoelectron spectroscopy (XPS). Blend films with controlled thickness were obtained by spin-coating polymer–toluene solutions with various concentrations. Films with thicknesses smaller and larger than the maximum wavelength of concentration fluctuations were considered. Morphology of the blend films was characterized during and after phase separation. The obtained peculiar morphology was related to surface enrichment with the lower-surface-energy component, as was verified by XPS analyses.