Nanopatterning in Langmuir-Blodgett monolayers of a thermoresponsive double hydrophilic block copolymer studied by atomic force microscopy.
The microphase-separation of Langmuir-Blodgett (LB) monolayers of a rhodamine B (RhB) end-labeled double hydrophilic block copolymer (DHBC), RhB-Poly(N,N-dimethylacrylamide)-b-poly(N,N-diethylacryl-amide) (RhB-PDMA(207)b-PDEA177) and the 1:1 segmental mixture of PDEA and RhB-PDMA homopolymers was followed by AFM. The DHBC LB films revealed a loose distribution of nano-aggregates with variable geometries below the lower critical solution temperature (LCST) of PDEA (32 degrees C) and low surface pressure (3 mN m(-1)). By increasing either the temperature above the LCST of PDEA or the surface pressure beyond the immersion regime of PDMA in the subphase (7 mN m(-1)) a dense nanopatterning was obtained. The absence of a corresponding regular nanopatterning in LB films of mixed homopolymers with the same composition highlights the role of the covalent bonding between PDEA and PDMA on the self-segregation of the two blocks at the air-water interface.
Interaction of a double hydrophilic block copolymer with lipid monolayers at the air–water interface
The interaction of poly(N,N-dimethylacryl-amide)-b-poly(N,N-diethylacrylamide) (PDMA207-b-PDEA177), (DHBC), with 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phospho-(1′-rac-glycerol) (sodium salt) (DPPG) and stearic acid (SA), was investigated at the air–water interface. The π − A isotherms of DHBC/DPPC and DHBC/DPPG binary mixtures are nearly the sum of the contribution of components weighted by the molar composition, — the additive rule. The π − A curves of the mixtures show a plateau at ~ 7 mN m− 1, owing to the immersion of the hydrophilic block PDMA, and other at ~ 27 mN m− 1 attributed to the immersion of the less hydrophilic PDEA block. Differently, the binary mixtures of DHBC/SA and PDEA homopolymer/SA do not follow the additive rule of the components showing an expanding effect at low surface pressures. Brewster angle microscopy images show that both DHBC and PDEA polymers interact with lipid monolayers, strongly disturbing their morphology.
Composite monolayer fabrication by an arc-spray process
A single layer (monotape) technique for fabricating complex high-temperature tungsten-fiber-reinforced superalloy composites is proposed. The fabrication of sheets of arc-sprayed monotape 38 cm wide and 122 cm long has been demonstrated. Composites fabricated using the method are shown to have equal tensile strength and a cleaner matrix than composites fabricated from powder metal cloth monotapes, and the present technique is less expensive than the powder metal fabrication techniques.