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The mutual miscibility of five binary ethylene/norbomene copolymers of the N(x)E(1-x)/N(y)E(1-y) type where x and y represent the norbornene content in the first and second copolymers, respectively (with x/y of 0.36/0.52, 0.36/0.56, 0.36/0.62, 0.46/0.60 and 0.46/0.66), in five different compositions was studied by rheology and differential scanning calorimetry. Most of the blends do not obey the principle of time-temperature superposition, i.e., they can be considered as thermorheologically complex, and hence immiscible. The experimental data from rheology were compared to a recent lattice cluster theory. The theoretical miscibility diagram correctly predicts the experimental cases for most blend compositions except for the very asymmetric compositions. (c) 2007 Elsevier Ltd. All rights reserved. Polymer

The phase behaviour of poly(n-butyl acrylate) gels swollen in smectic-A low molar weight liquid crystals (LMWLC) was investigated, in view of the increasing importance of such systems in advanced optical devices. Polyacrylate networks were prepared by ultraviolet (UV) irradiation of reactive formulations including a monomer (n-butyl acrylate), a crosslinker (hexane diol diacrylate, HDDA) and a photoinitiator (2-hydroxy-2methyl-1-phenyl-propane-1-one). The obtained dry polymer networks were characterized by a combination of physical techniques, and immersed in an excess of smectic-A LMWLC (4-n-octyl-4 � -cyanobiphenyl (8CB) and 4-n-octyloxy-4 � -cyanobiphenyl (8OCB)), forming polymer gels. A detailed study by polarized optical microscopy (POM) allowed us to determine the swelling degree of the gels and the phase behaviour of the solvent inside the polymer matrix in a wide range of temperature. It was found that the LC inside the swollen poly(n-butyl acrylate) networks remains isotropic, even if the surrounding solvent is liquid crystalline. The uptake of LMWLC inside the network preferentially takes place between the smectic to nematic and the nematic to isotropic transition temperatures of the solvent. Phase diagrams in the concentration–temperature framework were given and discussed as a function of crosslinking degree of the polymer network and temperature, and phase behaviour of the solvent. Finally, results were critically examined and compared to the few studies found in the literature.

MQ siloxane resins containing Si–H functions have been made from tetramethyldisiloxane and tetraethoxysilane. Hydrosilylations with mesogenic alkenes give low molecular weight liquid crystal MQ resins with potentially useful properties.

Structural relaxation processes in poly(methyl-para-tolyl-siloxane) (PMpTS) polymers of three molecular weights were studied using dynamic light scattering. Two relaxation processes: the usual alpha and an additional slow one alpha' were observed and studied as function of temperature and molecular weight. Contrary to the structural relaxation, we find that in a plot T-T-g the relaxation times for the alpha', process for all molecular weights do not collapse to a single curve. For one of the samples the light scattering correlation functions were compared with the corresponding functions obtained by means of mechanical relaxation, dielectric spectroscopy and computer simulations. The simulations show that the bimodal distribution, i.e. the alpha relaxation and the slow (a') process are contained in the correlation functions of most of the probes (optical anisotropy, dipole moment, chain bond, density) in agreement with experimental observations. (c) 2006 Elsevier Ltd. All rights reserved.

Liquid droplets in equilibrium with vapor are simulated at solidlike surfaces using the cooperative motion algorithm (CMA). These droplets behave like real droplets, i.e., the densities of the coexistent liquid and vapor phases obey empirical relations such as rho l - rho v proportional, variant (1 - T/Tc)(1/3). Droplet evaporation was studied under various interaction conditions, i.e., nonsoluble and soluble substrates. In the last case, substrate particles migrate toward the liquid-vapor interface to minimize the droplet surface energy. This leads to the formation of a microwell surrounded by a ringlike deposit on the substrate surface. It is shown that the ring formation in the first stages of evaporation results in pinning of the droplet contact area.

Calcium containing poly(urethane-ether)s (PUEs) were synthesized by the reaction of hexamethylene diisocyanate or toluylene 2,4-diisocyanate (HMDI or TDI) with a mixture of calcium salt of mono(hydroxybutyl)phthalate $[Ca(HBP)_2]$ and polyethylene glycol ($PEG_2_0_0$ or $PEG_4_0_0$). A series of calcium containing PUEs having different composition were synthesized by taking the mole ratio of $Ca(HBP)_2$:$PEG_2_0_0$ or $PEG_4_0_0$:diisocyanate (HMDI or TDI) as 3:1:4, 2:2:4 and 1:3:4 to study the effect of calcium content on the properties of the copolymer. The structure of the polymers were confirmed by IR, $^1H-NMR,$ $^13C-NMR,$ and solid state $^13C-CP-MAS$ NMR. The polymers were soluble in dimethyl sulfoxide and dimethyl formamide. The initial decomposition temperature of the polymers decreases with increase in calcium content. The $T_g$ value of PUEs increases with increase in calcium content and decreases with increase in soft segment content and length. A single $T_g$ value is observed for the calcium containing PUEs based on $PEG_2_0_0$ shows the presence of homogeneous phase. However, two $T_g$ values for the PUEs based on $PEG_4_0_0$ for various composition of $Ca(HBP)_2$, $PEG_4_0_0$ and diisocyanate (HMDI or TDI) shows the presence of heterogeneous phase. The viscosity of the calcium containing PUEs increases with increase in the soft segment content as well as its length and decreases with increase in calcium content. X-ray diffraction patterns of the polymers show that the HMDI based polymers are partially crystalline and TDI based polymers are amorphous in nature. The dynamic mechanical analysis of the calcium containing PUEs based on HMDI shows that at any given temperature modulus $(g^' and g^")$ increases with increase in the ionic content in the polymers.

New aromatic polyamides containing 1,3,4-oxadiazole or benzonitrile units in the main chain and 5-(4-acetoxybenzamido) groups in the side chain have been synthesized and their properties have been characterized and compared with those of related polyamides and polyoxadiazole-amides. These polymers show good thermal stability, with initial decomposition temperature being at about 300 °C and glass transition temperature in the range of 260–280 °C. They are easily soluble in certain solvents such as N-methylpyrrolidinone (NMP), N,N′-dimethylacetamide (DMA) and N,N′-dimethylformamide (DMF) and can be cast from solutions into thin flexible films. The polymer films had tensile strengths in the range of 77–97 MPa, tensile moduli in the range of 2.3–2.6 GPa and elongation at break values ranging from 6% to 24%. One of the polymers containing the 1,3,4-oxadiazole ring exhibited blue fluorescence.

Blends of functionalized polystyrenes (3NPS) having three dimethylamino groups {N(CH3)(2)} at one end, with sulfonic acid end-capped polyisoprenes (HO3SPI) were prepared in a ratio of N(CH3)(2)/ SO3H = 1. The morphology of these blends was studied by small-angle X-ray scattering and transmission electron microscopy and the associated dynamics by rheology. The results of the microdomain investigation, as well as of the associated dynamics, provide unambiguous evidence for controlled miktoarm star block copolymer formation via ionic interactions. Macromolecules

The solid columnar discotic and liquid crystalline (LC) phases formed by alkyl-substituted hexabenzocoronene (HBC) mesogens have been investigated by a combination of X-ray scattering and a variety of advanced solid-state NMR methods. Correlations between chemical structure, molecular packing and dynamics are established. Maximum charge carrier mobility is observed for a crystal-like stacking of the disks in the column with optimized π−π interactions. For systems with lower intracolumnar order the charge carrier mobility is slightly lower and slow axial motion of the disks around the column axes occurs.

The dynamic Monte Carlo WO simulation using algorithms based on the cooperative motion algorithm (CMA) is presented in application to analysis of structure and dynamics of single complex macro-molecules. Linear chains, polymer rings and polymer stars are considered. Relations between details of molecular dynamics in such systems and quantities which can be considered as observable in the dielectric relaxation measurements are presented and discussed in comparison with the existing experimental evidence.

The Dynamic Lattice Liquid (DLL) model for molecular rearrangements in liquids is discussed in application to both simple supercooled liquids and polymer melts. It is shown, that the model is able to reproduce a broad class of various temperature dependencies of relaxation times, lying between the extremal cases represented by the Arrhenius relation on one and by the Vogel-Fulcher-Tamman (VFT) relation on the other hand. Rates of rearrangements are considered as being controlled by thermal activation with activation energy barriers dependent on local density. Various dependencies of the activation energy barriers on local density are examined. All cases are based on the uniform microscopic picture of cooperative molecular rearrangements operating in a dense system under conditions of the excluded volume and continuity of the system. The model is implemented as a simulation algorithm, which is used to describe dynamic properties of liquids and polymer melts. Simulation results obtained for systems representing simple liquids as well as linear polymers, multiarm star polymers and microgels are presented. An analogy in the dynamic behavior between the low molecular liquids and melts of macromolecules with complex compact architectures is discussed.

In this paper, we demonstrate a computer simulation method allowing to study single model macromolecules with various complex topologies. The method is applied to branched macromolecules such as H-shaped polymers and polymer stars. Preliminary results describing both the structure and dynamics are presented.

Dielectric spectroscopy has been employed to study the local and global dynamics of polyisoprene in the asymmetric star (polystyrene)(polyisoprene) 2 (SI 2 ) and in the 3-miktoarm star terpolymer (polystyrene)(polyisoprene)(polybutadiene) (SIB). All measurements refer to the ordered phase where PS cylinders are embedded on the I and I/B matrix, respectively. Effectively, we are studying the local and global dynamics of tethered PI chains in two environments : one made by I-chains (SI 2 ) and another by the I/B-chains (SIB). At low temperatures, the PI local segmental dynamics in SI 2 and SIB are different, reflecting the modification of the local friction by introducing the faster PB chains in the latter. At higher temperatures, however, this effect diminishes due to the demixing of I and B. To explore the thermodynamic and mobility effects on the global dynamics, we have studied, respectively, a ternary blend composed of PI, PB, and PS and binary blends of SIB and SI 2 with short PB chains. The PI global dynamics in SI 2 and SIB resemble the dynamics of PI stars with additional entanglement effects in the latter.

The static and kinetic aspects of the order-disorder transition (ODT) in newly synthesized model 3-miktoarm star copolymer (simple graft) of SI2 type, (polystyrene)(polyisoprene) 2 , and a 3-miktoarm star terpolymer of SIB type, (polystyrene)(polyisoprene)(polybutadiene), have been studied using SAXS and rheology. The morphology and the order-disorder transition temperature (T ODT ) have been identified from the two-dimensional SAXS patterns with shear-oriented samples. Hexagonally ordered cylindrical microdomains aligned along the direction of shear and with T ODT =379 K have been formed for both samples studied. The SAXS profiles at temperatures well above the T ODT have been fitted to the mean-field theory (MFT) for graft copolymers. Near the ODT deviations from the theory have been observed and the SAXS data provide unambiguous evidence for the existence of fluctuations. The T ODT obtained from rheology is in excellent agreement with the one from SAXS. Discontinuities in the SAXS peak intensity and in the storage modulus near the T ODT are more pronounced in these systems as compared to linear diblocks. The ordering kinetics have been studied with rheology and complementary with SAXS. The width of the kinetically accessible metastable region is enlarged as compared to linear diblocks. For shallow quenches the ordering proceeds by heterogeneous nucleation and growth of three-dimensional grains with cylindrical microstructure. Our kinetic studies probe the metastable states near but below the T ODT

SAXS and pressure-volume-temperature (PVT) measurements are employed in bulk and plasticized poly(cyclohexyl methacrylate) (PCHMA) in the temperature range 252-448 K and provide a way of separating the density from the concentration fluctuations. It is shown that the density fluctuations are suppressed in the mixtures and that the concentration fluctuations increase with plasticizer content. Rayleigh-Brillouin scattering was also employed on the same mixtures, and the contribution of propagating density fluctuations (phonons) to the total fluctuations was evaluated at T above and below the T g

SAXS is employed to measure the density fluctuations in Bisphenol A polycarbonate (BPA-PC) and tetramethyl-Bisphenol A polycarbonate (TMPC) as a function of temperature (T) in the range 300-510 K. Pressure-volume-temperature (PVT) measurements are made for TMPC in the range 300-539 K and for applied pressures up to 200 MPa. WAXS measurements are performed for both polymers in the range 300-480 K. Using these techniques we characterize the state of order in the two polymers. Whereas from specific volume and WAXS measurements an estimate of the average free volume is obtained, SAXS provides the fluctuations in the free volume

Blends of the nematic liquid crystal E7 and poly(methylphenylsiloxane) (PMPS) with molecular weight 120,000 g/mol are investigated by high performance liquid chromatography (HPLC) measurements. This study was prompted by observations made recently while analyzing the phase behavior of poly(siloxane)/E7 and poly(acrylate)/E7 systems. A remarkable increase of the nematic to isotropic transition temperature TNI was found when polymer was added to the liquid crystal. Surprisingly, the increase of TNI was enhanced with the polymer concentration up to 80 wt%, where it reached its highest value. This behavior could be interpreted by invoking a preferential solvation of the constituents of E7 towards the polymer. The present investigation provides an evidence of this phenomenon using HPLC data. q 2004 Elsevier Ltd. All rights reserved.

We investigated the generation dependent shape and internal structure of star-burst dendrimers under good solvent conditions using small angle x-ray scattering and molecular modeling. Measurements have been performed on poly(amidoamine) dendrimers with generations ranging from g=0 up to g=8 at low concentrations in methanol. We described the static form factor P(q) by a model taking into account the compact, globular shape as well as the loose, polymeric character of dendrimers. Monomer distributions within dendrimers are of special interest for potential applications and have been characterized by the pair correlation function gamma(r), as well as by the monomer and end-group density profile, rho(r) and rho(e)(r), respectively. Monomer density profiles and gamma(r) can be derived from P(q) by modeling and via a model independent approach using the inverse Fourier transformation algorithm first introduced by Glatter. Experimental results are compared with computer simulations performed for single dendrimers of various generations using the cooperative motion algorithm. The simulation gives direct access to gamma(r) and rho(r), allows an independent determination of P(q), and yields in addition to the scattering experiment information about the distribution of the end groups. Excellent qualitative agreement between experiment and simulation has been found.

We have studied the effect of zwitterion (Zw) substitution on asymmetrically functionalized copolymers of the type ZwIS, ZwSI (where I is polyisoprene and S is polystyrene), and of diblock and triblock copolymers functionalized at both ends (ZwISZw) and junctions (SZwIZwS), respectively. We have employed SAXS, rheology and dielectric spectroscopy to study the structure and dynamics. The positioning of the short but strongly incompatible polar group with respect to the S and I blocks strongly affects the structure and dynamics of the material because of aggregation. The aggregation strongly modifies the electron density profiles, which reflects in the alteration of the SAXS spectra. The most pronounced effects are found when the functional group is located within the center of the domain with the lowest electron density (polyisoprene).

The order−disorder transition (ODT) and the ordering kinetics have been studied in four-arm star diblock copolymer melts of styrene (corona) and isoprene (core) by rheology and SAXS. The results are compared with the corresponding linear diblock and show that the transition shifts in the direction predicted by theory. The mean-field structure factor is used to describe the SAXS profiles at T ≫ TODT and to extract the temperature dependence of the interaction parameter χ(T). Because of the weak T dependence of χ, we can explore only a small region of the phase diagram, namely, 16.5 < χN0 < 14.6, for fPS = 0.25. The microphase-separated state consists of spherical microdomains of the minor component (PS) which resembles a bcc phase, however, not with the full symmetry. To explore the morphology over a broader T range, we use the results of computer simulation on equivalent chains, which for fPS = 0.25 provide the following succession of phases: hexagonal − a bicontinuous structure which resembles the gyroi...

Dielectric relaxation spectroscopy has been used to investigate the block end-to-end vector relaxation in symmetric poly(styrene-b-1,4-isoprene) diblock copolymers both in the ordered state and in ...

Two cylinder-forming polystyrene-block-polybutadiene block copolymers of type A-B with antisymmetric composition (polymer P1 with A : B = 3 : 1 (w/w) and polymer P2 with A : B = 1 : 3 (w/w)) and their binary mixture were studied by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) in order to determine the microphase structure. The cylindrical microstructure is confirmed for both copolymers, whereas, in the mixture, both techniques have unambiguously shown that a regular lamellar structure is obtained at the polymer-polymer composition P1 : P2 = 1 : 1 (ratio of the numbers of chains). Qualitatively, the same results are obtained for corresponding systems simulated by the cooperative motion algorithm (CMA). Direct observations of the structure as well as the cooperative structure factors determined in the strong segregation limit for the simulated systems indicated lamellar structures in the blend of composition P1 : P2 = 1 : 1, in contrast to the microfibrillar morphology of the copolymers. The simulation additionally indicated a polymer-polymer microseparation. The experimental and simulation results are compared with theoretical predictions based on the self consistent field theory. Macromolecular Chemistry and Physics

Cycloolefin copolymers of ethylene and norbornene, with norbornene content in the range from 36 to 62 mol %, were studied with respect to the thermal, thermodynamic, and rheological properties using differential scanning calorimetry, pressure-volume-temperature, and dynamic mechanical measurements. All copolymers obey the principle of time-temperature superposition, i.e., they can be considered as thermorheologically simple except for a temperature range in the vicinity of T-g. Despite this, the results on (i) the ratio of activation energies E-V(*)/H-* used to quantify the origin of the liquid-to-glass transition, (ii) the pressure coefficient of the glass temperature T-g(P), and (iii) the dynamic fragility m suggest increasing dynamic heterogeneity with increasing norbornene content that is driven by the structural heterogeneity along the backbone. (c) 2006 American Institute of Physics. Journal of Chemical Physics

We measured the form factor of bottle-brush macromolecules under good solvent conditions with small-angle neutron scattering and static light scattering. The systems under investigation are brushes, synthesized via the grafting-from route, built from a poly(alkyl methacrylate) backbone to which poly(n-butyl acrylate) side chains are densely grafted. The aim of our work is to study how the systematic variation of structural parameters such as the side chain length and backbone length change the conformation of the polymer brushes in solution. All spectra can be consistently described by a model, considering the bottle-brush polymers as flexible rods with internal density fluctuations. Parameters discussed are (1) the contour length per main chain monomer l(b), (2) the fractal dimension of the side chains Ds, as well as (3) the fractal dimension D, and (4) the Kuhn length lambdak of the overall brush. l(b)=0.253+/-0.008 nm is found to be independent of the side chain length and equal to the value found for the bare main chain, indicating a strongly stretched conformation for the backbone due to the presence of the side chains. The fractal dimension of the side chains is determined to be Ds=1.75+/-0.07 which is very close to the value of 10.588 approximately 1.70 expected for a three-dimensional self-avoiding random walk (3D-SAW) under good solvent conditions. On larger length scales the overall brush appears to be a 3D-SAW itself (D=1.64+/-0.08) with a Kuhn-step length of lambdak=70+/-4 nm. The value is independent of the side chain length and 46 times larger than the Kuhn length of the bare backbone (lambdak=1.8+/-0.2 nm). The ratio of Kuhn length to brush diameter lambda(k)d>or=20 determines whether lyotropic behavior can be expected or not. Since longer side chains do not lead to more persistent structures, lambda(k)d decreases from 8 to 4 with increasing side chain length and lyotropic behavior becomes unlikely.

Two new mechanical models for the description of mechanical properties of two-component polymer blends are proposed. On the basis of these models the dependence of the dynamic complex moduli on the blend content is theoretically calculated. Results obtained theoretically are compared with experimental data for polyethylene and polypropylene blends.

Dynamic birefringence and dynamic light scattering techniques have been used to characterize the morphological changes in low-density polyethylene during sinusoidal deformation with various frequencies at constant temperature. Measurements have been conducted on samples with various morphologies. Two separate relaxation processes in the frequency range from 0.003 to 20 cps have been found to be strongly dependent on the morphology (i.e. spherulite perfection, degree of orientation correlation and sizes of crystalline elements) and less dependent on crystallinity of samples. By comparison of the results with calculated stress distribution inside spherulite mechanical model, the locations of distinguished relaxation processes in particular morphology elements have been discussed.

The theoretical backgrounds of the method of spherulite size distribution determination, on the basis of the small-angle light scattering technique, are presented. Special corrections of experimental data are introduced to achieve great accuracy of the determination of scattered light intensity distribution. Experiments have been done on low-density polyethylene samples obtained in various crystallization conditions. For these samples, the stepwise distributions of spherulite size have been determined.

Small-angle light scattering technique has been used to record changes in spherulite size during non-isothermal crystallization of low-density polyethylene under different cooling conditions. From these changes, the spherulite growth rates at various temperatures in the range 72–91° have been determined. The results are discussed on the basis of the Hoffman Lauritzen theory.