Nanostructured blends of poly(methylmethacrylate) and polyamide-6 (PMMA/PA6) were prepared by reactive blending. The grafting reaction occurs between the amino end-group of PA6 and glutaric anhydride units randomly distributed along the backbone of PMMA. Short PA6 grafts were used to facilitate reaction at the interface. Very fine morphologies were obtained after blending. Annealing the blends above the melting point of polyamide reveals that the amount of anhydride present on PMMA chains controls self assembly of the blends and stability of the copolymer at the interface. In some cases, stable swollen lamellar assemblies were achieved. These materials exhibit interesting properties such as transparency, creep resistance and solvent resistance.

A century-old puzzle on the apparent contradiction that some materials disorder as they are cooled gains universality following new observations of closed-loop phase behaviour in a block-copolymer system.

Part 1 of these studies described poly(methyl methacrylate-r-polyoxyethylene methacrylate) P(MMA-r-POEM) comb polymers that present Arg-Gly-Asp (RGD) peptides at a surface in nanoscale clusters on a protein-resistant background for control of cell adhesion. Here in part 2, we examine surface segregation of these peptide-modified and unmodified comb polymers blended with polylactide (PLA) as a self-assembly approach suitable for surface modification of porous tissue engineering scaffolds. Multiple thermodynamic driving forces for surface enrichment of the comb polymer are exploited by annealing PLA/P(MMA-r-POEM) blends above the glass transition of the blend components but below the melting point of PLA, while in contact with water. Predictions of the interfacial composition profiles of annealed blends were made using a self-consistent field (SCF) lattice model. The calculations predict strong enrichment of the comb in the top approximately 50 A of blends, and organization of comb molecules in quasi-2D conformations at the interface, similar to the apparent structure of pure comb surfaces in contact with water described in part 1. Experimentally, PLA/comb blend surfaces were characterized by contact angle measurements, XPS, quantification of ligand-cluster surface density and stability by AFM and fluorescent nanosphere labeling, and cell attachment assays. These data were consistent with SCF predictions, showing significant enrichment of the comb at water-annealed surfaces and RGD cluster densities consistent with 2D conformations for comb molecules in the surface layer. Bulk miscibility of the blends was verified by dynamic rheometry, small-angle neutron scattering, DSC and X-ray diffraction studies. Surface segregation of combs provided tunable cell adhesion on PLA through surface-localized nanoclusters of RGD atop a cell-resistant background.

The lower critical ordering of diblock copolymers is an entropically driven phase transition that is accompanied by a negative volume change on mixing. Small angle: neutron scattering (SANS) studies of the phase transition under hydrostatic pressure has shown a very large pressure coefficient delta T/delta P = 147 degrees C/ kbar. Differential scanning calorimetry studies of the phase transition show that the transition from the disordered to the ordered state is endothermic: with an enthalpy, Delta H similar to 0.2 J/g. X-ray reflectivity studies of thin copolymer films as a function of temperature exhibits the characteristic thermal expansion of the copolymer film with a discrete change in the film thickness at the transition that corresponds to a 0.35 % volume change. This agrees, within the same order of magnitude, with what would be predicted from the Clapeyron equation.

The effect of hydrostatic pressure on the lower critical ordering transition (LCOT) was investigated by in situ small angle neutron scattering on symmetric and asymmetric diblock copolymers of perdeuterated polystyrene and poly(n-butyl methacrylate). These systems exhibit a transition from the disordered to ordered state upon heating. Similar to the lower critical solution transition (LCST) in polymer mixtures, the LCOT is entropically driven and is accompanied by an increase in volume on demixing of the copolymer blocks. As a consequence, application of hydrostatic pressure markedly increases the temperature at which the transition from the disordered to the ordered state occurs. Small angle neutron scattering studies as a function of temperature and pressure show that the pressure dependence of the LCOT, Delta T-LCOT/Delta P, is up to +147 degrees C/kbar (1.45 +/- 0.07 degrees C/MPa), roughly 1 order of magnitude greater than that seen at elevated pressures for diblock copolymers exhibiting an upper critical ordering transition (UCOT). Additionally, SANS data obtained at various pressures were superimposed to generate master curves for the peak intensity, peak position, and full width at half-maximum (fwhm). This suggests an equivalence between temperature and pressure of the thermodynamic behavior of systems that exhibit the LCOT.

The processing parameters for achieving proper control of the kinetics of interface reaction even in very reactive systems are discussed. The work concentrates on composites consisting of a pure Al matrix reinforced by continuous fibres of Inconel 601. Use is made of a low thermal inertia squeeze casting set-up equipped with monitoring of the sample temperature. Microstructural characterization and DTA analysis allow to elucidate some aspects of the reaction mechanisms. A model based on a parabolic growth law is developed for ranking the severity of processing conditions.