Critical Interaction Strength for Surfactant-Induced Mesomorphic Structures in Polymer−Surfactant Systems

Abstract

The critical interaction strength to induce mesomorphic structures in flexible polymers by complexing with surfactants is determined by using surfactants with different hydrogen-bonding strengths. Two essential requirements have to be satisfied: (i) the association has to be strong enough, otherwise the structure dissociates. (ii) The polar-nonpolar repulsion has to be sufficiently strong to induce microphase separation. If the latter requirement is not satisfied, but the association is sufficiently strong, a characteristic comb polymer-like SAXS peak will still be present in the homogeneous melt state. To address these issues experimentally, poly(4-vinylpyridine) (P4VP) was combined with different classes of hydrogen-bonding surfactants: alkyl aromatic alcohols, alkyl carboxylic acids, alkyl aliphatic alcohols, and alkyl aliphatic amines. FTIR, SAXS, WAXS, and optical microscopy demonstrate that alkyl aromatic alcohols, such as 1-dodecyl 3,4,5-trihydroxybenzoate yield mesomorphic structures at not too high a temperature. Alkyl carboxylic acids are somewhat less effective. In the melt state, the SAXS data still show a peak, but because no birefringence could be found, the peak is attributed to block copolymer-like concentration fluctuations in an otherwise homogeneous state. Aliphatic alkyl alcohols yield still weaker hydrogen bonding. In the melt the short alkyl aliphatic alcohol surfactants form a homogeneous mixture with P4VP, but a SAXS peak is no longer observed. The longer ones macrophase separate. Both the alkyl carboxylic acids and the short alkyl aliphatic alcohols partly macrophase separate at lower temperatures due to crystallization.

On lyotropic behavior of molecular bottle-brushes: A Monte Carlo computer simulation study

“…The main chain beads from which a side chain is grafted were chosen equally along the backbone, i.e., every other main chain bead carried a side chain. Side chains of lengths M ϭ 0, 4,6,8,10,12,16, and 20 were considered. The initial conformation was created in the following way.…”

“…Another related but quite different set of systems was obtained by various groups in a much simpler way using strong physical association between end-functionalized oligomeric chains and homopolymers. [3][4][5][6][7][8][9][10][11] Compared to the former systems, the oligomeric side chains used so far are, however, considerably smaller.…”

Micro- and macrophase separation in blends of reversibly associating one-end-functionalized polymers

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] The phase behavior of polymer systems is dominated by the ubiquitous unfavorable interactions between unlike species. In the case of polymer blends this usually leads to undesirable macrophase separation.…”

Supramolecular routes towards liquid crystalline side-chain polymers

“…Subsequent work with PVP and various hydrogen bond donating amphiphiles showed four regimes, outlined in Table 1, according to surfactant-polymer repulsion and hydrogen bond strength. 29 Thus, the judicious choice of polymer and surfactant can be used to tune material properties.…”