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.
Surface Micelle Structures and Monolayer Compression Moduli of Double Hydrophilic Block Copolymer
At the air/water interface, amphiphilic block copolymers are well-known to form typical surface micelles composed of hydrophobic block cores and hydrophilic block coronas. However, the micelle/aggr...
A.C. and D.C. conduction in lightly substituted anthracene Langmuir films
Abstract The a.c. and d.c. properties of short-chain derivatives of anthracene prepared by using the Langmuir-Blodgett technique are reported; these thin films display interesting conduction effects on account of their unusual molecular structure. Emphasis is placed on the 9-alkyl-10-anthrylpropionic acid derivatives in which the alkyl chain is either C4H9 (C4 anthracene) or C6H13 (C6 anthracene). As expected, the dark conduction properties are markedly different from those of unsubstituted crystalline anthracene. For example, there is a marked anisotropy in the conductivity of C4 anthracene, the in-plane value exceeding that in a direction perpendicular to the layers by a factor of 108. By use of appropriate electrodes double injection effects accompanied by blue light emission were found. The admittance data for these novel films differ slightly from those of films of conventional fatty acid salts.