Chain conformation and dynamics in spin-assisted weak polyelectrolyte multilayers.

We report on the effect of the deposition technique on film layering, stability, and chain mobility in weak polyelectrolyte layer-by-layer (LbL) films. Ellipsometry and neutron reflectometry (NR) showed that shear forces arising during spin-assisted assembly lead to smaller amounts of adsorbed polyelectrolytes within LbL films, result in a higher degree of internal film order, and dramatically improve stability of assemblies in salt solutions as compared to dip-assisted LbL assemblies. The underlying flattening of polyelectrolyte chains in spin-assisted LbL films was also revealed as an increase in ionization degree of the assembled weak polyelectrolytes.

Molecular Weight Dependence of Polymer Chain Mobility within Multilayer Films.

Fluorescence recovery after photobleaching has been applied to determine, to our knowledge for the first time, the molecular weight () dependence of lateral diffusion of polymer chains within layer-by-layer (LbL) films. As shown by neutron reflectometry, polyelectrolyte multilayers containing polymethacrylic acid (PMAA, / < 1.05) of various molecular weights assembled from solutions of low ionic strengths at pH 4.

Multiresponsive clay-containing layer-by-layer films.

We report on polymer/clay layer-by-layer films responsive to multiple stimuli. Temperature- and salt-responsive films were constructed using assembly of poly(N-isopropylacrylamide) (PNIPAM) and montmorillonite clay nanosheets. An additional pH response was achieved by depositing and cross-linking hybrid, dual-network PNIPAM/clay/PNIPAM/poly(methacrylic acid) (PMAA) multilayers.

Hydrogen-bonded layer-by-layer films of block copolymer micelles with pH-responsive cores.

We report on construction of hydrogen-bonded monolayers and multilayers of micelles of the poly(2-(diethylamino)ethyl methacrylate)-block-poly(N-isopropyl acrylamide) (PDEA-b-PNIPAM) with PNIPAM-corona and polybasic PDEA cores. Films were constructed at pH 7.5 and 25°C to assure the deposition of PDEA-b-PNIPAM in the micellar form.

Hydrogen-bonded layer-by-layer temperature-triggered release films.

A hydrogen-bonded layer-by-layer (LbL) technique was used to build multilayers of neutral, temperature-responsive polymers such as poly(N-isopropylacrylamide) (PNIPAM), poly(N-vinylcaprolactam) (PVCL), poly(vinyl methyl ether) (PVME), or poly(acrylamide) (PAAm) with a polycarboxylic acid such as poly(acrylic acid) (PAA), poly(methacrylic acid) (PMAA), or poly(ethacrylic acid) (PEAA). For all multilayers involving temperature-responsive polymers, the temperature used during or after self-assembly had a significant effect on film stability with pH changes. The proximity of the self-assembly or post-self-assembly temperature to the critical temperature of phase separation of a neutral polymer from solution resulted in a higher pH stability of multilayers.