Blends of a thermotropic liquid crystalline polymer (TLCP) and a thermoplastic matrix were compounded. Upon subsequent injection moulding and spinning, the TLCP was deformed into fine fibrils in the matrix, giving in-situ reinforcement. Especially after spinning, the composite fibres contain fibrils with very high aspect ratio, and exhibit mechanical properties in accordance with simple composite models for modulus and strength.

Mixtures of a rodlike and a flexible polyimide were prepared by solution-blending of the respective poly(amic alkyl ester) and poly(amic acid), followed by solvent evaporation and thermal imidization. The size scale of the phase separation, as measured by light scattering, is primarily set during the demixing of the precursor polymers, with no significant coarsening observed due to the imidization performed at 400°C. The observed variation of the domain size with parameters such as composition, molecular weight and film thickness is discussed in terms of the miscibility of the precursor polymers as well as the thermal history to which these were exposed.

This work represents a continuation of earlier studies of blends of polymer liquid crystals (PLC) with ordinary engineering polymers (EP). We now focus on connections between mechanical and other properties and phase structures and phase diagrams. Pure PLC are already two-phase systems; in each case addition of an EP complicates the situation further. In particular, we are concerned with phases which we call quasi-liquids, at temperatures between the glass transition and the melting point. Quasi-liquids do not have the mobility usually associated with liquids - because of the presence of other constituents and also because of orientational effects produced by the mesogenic groups. In phase diagrams of PLC-containing systems one should also take into account non-equlibrium phases. We are trying to show how such diagrams make possible Intelligent processing and a better control of properties of the PLC + EP materials.

The investigation of the thermal behavior of polymer blends leads to phase diagrams which involve Important information about the system. From these diagrams, equilibrium as well as non-equilibrium phases can be deduced and ranges of miscibility or partial miscibility of the polymers become obvious. Hence the diagrams are of a great value for processing of advanced polymer blends, especially If a polyphasic polymers such as a polymer liquid crystal is one of the constituents of the system.

To determine the compatibility between the rigid rod and the flexible chain polyquinolines, both small angle x-ray and neutron scattering measurements were conducted on blends containing deuterated flexible chains. The scattering intensities from both x-ray and neutron were reduced to their absolute scales in order to remove the scattering contribution from microvoids which tended to overshadow the signal of molecular origin. Quantitative information regarding the molecular dispersion in a 50/50 rigid rod and flexible chain blend was obtained. The result indicated that this material was partially segregated but not to the point of single component phases.

Blends of polybenzimidazole (PBI) with either of two fluorine-containing polyimides were prepared by casting from solution and by precipitation. Dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC) were used to study miscibility in the two blend systems.

The blends of PBI with the first polyimide, the polysulfonimide Pl-1, consisted of a single phase when the blends contained less than 30 wt% Pl-1; above 50 wt% Pl-1, phase separation occurred even at room temperature. The PBI blends containing the second polyimide, Pl-2, were immiscible.

Small angle neutron scattering (SANS) has been used to study the scattering function and thermodynamics of blends of linear protonated polystyrene (PSH) and crosslinked deuterated polystyrene (PSD). Two series of samples were synthesized. In both cases the samples were made by dissolving the linear PSH in deuterated (d8) styrene monomer containing a small amount of divinyl benzene as a crosslinker which was then polymerized to form the PSD network around the linear PSH chains. The samples were all made at a concentration of 50/50 by weight PSD/PSH. A special effort was made to keep the samples single phase so that SANS could be used to study the thermodynamics of the system and compare with theory. This entailed working at relatively low crosslink densities (<1 mole % crosslink units). Series 1 is a set of samples with the same crosslink density varying the length of the linear chain. Series 2 is a set of samples containing the same length linear chain varying the crosslink density systematically. By extrapolating S(q) obtained from SANS to q=O the zero angle scattering, S(O), was obtained. S(O) is inversely proportional to the second derivative of the free energy with respect to composition, ∂2 (Δf/kT)/∂ø2. Assuming additivity of the free energies of mixing and elasticity, the portion of the zero angle scattering due to elasticity is calculated.

Time-resolved light scattering has been employed to elucidate the dynamics of phase segregation of poly-p-phenylene terephthalamide (PPTA)/ amorphous nylon (AN) molecular composites. Miscible PPTA/AN blends can be prepared from sulfuric acid solution by rapidly coagulating the solution in distilled water. The composites, however, undergo phase segregation upon thermal treatment and exhibit a miscibility window reminiscent of a lower critical solution temperature (LCST). Several temperature-jump experiments were undertaken from ambient to a two-phase temperature region of 240, 250 and 260°C. Time-evolution of scattering profiles are analyzed in accordance with non-linear and dynamical scaling theories.

The versatility of polymeric blends is reflected in the range of usable end properties that can be achieved through alterations in the composition and/or effective control of the morphologies of the mixtures. Solvent cast and melt mixed blends of SAN and PMMA have been studied to understand the Influence of PMMA tacticity and the acrylonitrile content of the SAN copolymer on their phase behavior. The results show a shifting of the cloud point curves and the miscibility windows for the blends of SAN with different stereo-regular PMMAs. This is interpreted as being due to specific interactions between the acrylonitrile and methacrylate groups. The ‘goodness’ of mixing in the melt mixed blends were determined by FTIR ATR spectroscopy. The effects of the processing conditions on the mixing characteristics and subsequent improvement in mechanical properties are discussed. The limits of mixing that can be achieved using standard mixing procedures and their role in affecting the end use properties such as the flexural strength will also be discussed.

Dielectric and enthalpic relaxation times have been measured as a function of composition and temperature. A fractional exponential (W–W) distribution of relaxation times fits both the dielectric and enthalpic relaxation times with different values which are a function of composition. Free volume parameters calculated using the WLF equation are not simple functions of the composition. Concentration fluctuations are considered to be important in these phenomena.

We have studied the phase compatibility of simultaneous interpenetrating polymer networks poly (2,6–dimethyl–l,4–phenylene oxide) with a number of other polymer networks as a function of their solubility parameters. Even when the blends of the corresponding linear chain polymers are immiscible their interpenetrating polymer networks can be miscible in all proportions. We have also prepared the corresponding pseudo (or semi) interpenetrating polymer networks where one component is linear and in one system the polymeric catenanes. All these systems generally show microphase separation.

The morphology of ionomers, e.g., poly(ethylene-methacrylic acid) (EMA) lead salts (EMA/Pb) and lead sulfide compounds (EMA/PbS), has been studied by using the techniques of small angle x-ray scattering (SAXS), anomalous SAXS (ASAXS), wide angle x-ray scattering (WAXS), and differential scanning calorimetry (DSC). EMA/Pb containing less than 5 wt% of lead exhibited two characteristic SAXS peaks which corresponded to the lamellar structure of the partially crystalline polymer matrix and the ionic structure of the lead aggregates that were present in the amorphous regions. The lead aggregates were not distributed uniformly and increased in packing density with increasing lead content. Both DSC and WAXS showed that the crystalline phase was present for all EMA/Pb samples and that the crystallinity decreased slightly with increasing lead content. ASAXS near the L3 absorption edge of lead permitted the extraction of the scattered intensity of lead ions from the SAXS patterns of the superimposed crystalline and ionic structures. Correlation function analysis revealed that the ionic aggregates of the EMA/Pb containing 5 wt% of lead could be described by a liquid-like model with a short range order of 2-4 nm. EMA/PbS samples were made by a reaction of EMA/Pb ionomers with hydrogen sulfide. Instead of an ionic peak as shown by EMA/Pb samples, the SAXS patterns of EMA/PbS showed a broad diffraction peak located at the same q value as the lamellar peak of the EMA in acid form. The (lamellar) peak could be attributed to the interference between the PbS crystallites in the neighboring lamellae.

Exciton-exciton and exciton-excimer triplet fusion kinetics is monitored in medium molecular weight P1VN/PMMA solvent cast films with concentrations from 0.005 to 100% (weight), at temperatures of 77 to 300 K, via time resolved fluorescence and phosphorescence (10 ns to 10 sec). The heterogeneity exponent (h) is 0.5 for isolated P1VN chains, zero (classical) for pure P1VN and “fractal-like” throughout certain concentration regimes. However, h is not monotonic with blend concentration but rather oscillates between zero and 0.5. Correlation is made with morphology changes (phase separation, filamentation). As expected, the triplet exciton kinetics is dominated by short-range hops (about 5 A) and thus monitors the primary topology of the chains. At concentrations below 0.01%, the excitons are constrained to a truly one-dimensional topology. At higher concentrations there is a fractal-like topology. Similar studies were conducted on naphthalene-doped PMMA (1-20% weight). The lower concentration samples are neither segregated nor random solution phases.

We report the observation of the ordered bicontinuous double diamond (OBDD) structure in binary blends of poly(styrene-isoprene) diblock copolymer and homopolystyrene. The overall polystyrene volume fraction range is 64 - 67 PSvol% for the OBDD structure in binary blends of a lamellar diblock (SI 27/22) and a homopolymer (14.0 hPS). This composition range is approximately within the polystyrene volume fraction range established for pure diblock copolymers in the strong segregation regime having the OBDD structure. Ordered lamellae are observed at approximately 65 PSvol% when the homopolystyrene molecular weight is greater than the molecular weight of the polystyrene block of the copolymer. This observation is discussed in terms of the decreased degree of mixing between the homopolymer and the corresponding block and the resultant effect on the interfacial curvature.

The article deals with the phase diagram and spinodal decomposition of two polymers blends, namely d—PS/PVME and d(deutero)—PS/PS, investigated by small angle neutron scattering (SANS). The result of the static experiments is the excess free energy and the phase diagram. This is used as a basis for studies of non—equilibrium phenomena as spinodal decomposition. In polymer blends the Cahn—Hilliard—Cook theory of the early state of spinodal decomposition can be tested easily, because the blends have rather low relaxation rates; and they are meanfield systems [2,6] which makes interpretation simple, except in a very narrow temperature region near the critical point [6]. The kinetics in the isotopic blend d—PS/PS are so slow that the early states of spinodal decomposition can be studied within minutes. The presented SANS results have been performed at the KWS I small angle instrument at the FRJ—2 reactor in the KFA Jülich.

The mechanical properties and structure of melamine formaldehyde (MF)/poly(vinyl alcohol) (PVA) composites were studied in this paper. When PVA content was less than a certain value(about 20 weight %), both flexible strength and impact resistance were improved obviously. While the impact resistance improvement remained the previous trend the flexible strength didn't increase so rapidly as before when the PVA content was more than 20%. The morphology and reactivity of the prepolymer powder and the morphology of the finished specimens were investigated by means of microscope, infrared spectrum and transmission electron microscope(TEM). The results indicated that molecular composite structure was formed in this two-component system. The well-distributed PVA in this system was beneficial to the formation of the molecular composite structure. That could explain the effects of PVA on the mechanical properties and showed that the molecular composite structure are favourable for making full use of the macromolecular potentiality.

When suitable catalysts are molecularly dispersed in polymers, the polymers can be modified without added solvent. This paper describes studies on the morphology of samples of trans-l,4-polybutadiene and syn-1,2-polybutadiene which have been partially deuterated in the bulk. The development of a peak in the SANS data for the 1,2-polybutadiene suggests the formation of small domains upon deuteration. Possible explanations for this observation, including chemical and physical heterogeneity, are evaluated. Results of SAXS and thermal measurements are also considered.

Organic aerogels have been formed from the aqueous, sol-gel polymerization of resorcinol with formaldehyde. These materials are transparent and have continuous porosity with cell/pore sizes of less than 1000 Å. Their microstructure is composed of interconnected colloidal-like particles with diameters of 30-200 Å. The particle size, cell size, surface area, and density of the aerogels are predominantly controlled by the catalyst concentration used in gel preparation.

A versatile procedure was developed for synthesis of acrylic comb-like copolymers in three steps: (1) Hydroxyl terminated oligomers were synthesized from methyl methacrylate, butyl acrylate and glycidyl acrylate by free-radical initiated addition polymerization using a functional chain transfer agent, 2-mercaptoethanol, and very low initiator levels. (2) The oligomers were converted to macromonomers by reaction with isocyanatoethyl methacrylate. (3) The macromonomers were polymerized by free-radical initiation. Conditions during the first stage must be carefully selected to minimize formation of difunctional material which could cause gelation in the third stage. A variety of structures can be made such as comb-like copolymers with homopolymer tines or comb-like homopolymers with copolymer tines. Functional groups can be introduced by copolymerizing glycidyl acrylate into the macromonomer. Assignment of comb-like structures is not rigorously proven but is strongly supported by the synthetic route and by DSC, FT-IR and chromatographic data.

A block copolymer consisting of liquid crystalline polyester segments and methylated polyamide segments has been synthesized. Solution polycondensation of acid chloride end-capped poly(terephthaloyl phenylhydroquinone) (LCP portion) with an amine terminated poly(N,N'-dimethylethylene sebacamide) was utilized to prepare the block copolymer. Characterization by differential scanning calorimetry, infrared spectroscopy, thermogravimetric analysis, optical microscopy and elemental analysis has been performed to verify the existence of the block copolymer that may have potential as a molecular composite material or self-reinforcing thermoplastic.