Influence of Substrate Properties on the Topochemical Polymerization of Diacetylene Monolayers

Abstract

The influence of the underlying substrate on the UV initiated polymerization of diacetylene lipid monolayers was investigated using absorption spectroscopy and Brewster angle microscopy (BAM). The lipid/substrate affinity was tuned through choice of lipid headgroup as well as substrate properties. Lipids with positively charged headgroups, which readily polymerized in both blue (6 °C) and red (16 °C) polymer forms at the air/water interface, failed to polymerize when transferred to glass or hydrophobic glass (headgroups facing ambient) at either temperature. BAM analysis revealed that the diacetylene film was disordered on hydrophobic glass, which likely impeded the topochemical polymerization. On glass, however, BAM showed a highly crystalline film identical to that seen at the air/water interface, suggesting that strong interactions between the positively charged lipid headgroups and the glass inhibited polymerization in this case. In agreement, when the lipid/substrate interactions were reduced, either by introducing a cadmium arachidate bilayer between the diacetylene film and the glass or by substituting mica for glass, a limited polymerization occurred, forming the red film exclusively. As a further test, monolayers of acidic diacetylene lipids were deposited on glass. In this case polymerization was possible in both blue and red forms but diminished as the transferred film was aged. These results suggest that a strong lipid/substrate affinity may impede the topochemical polymerization, possibly by restricting the mobility of the lipids. By investigating polymerization as a function of substrate and headgroup chemistry, several factors influencing the lability of diacetylene films toward topochemical polymerization are presented.

Sharp Spherical Focal Spot by Dark Ring 4Pi-Confocal Microscopy

“…2c and d. Fig. 4 displays its experimental counterpart obtained through scanning a fluorescent polydiacetylene LB-monolayer on a standard glass cover slip [7,8]. The experimental result impressively confirms the theoretical prediction.…”

Photopolymerization of Diacetylene Lipid Bilayers and Its Application to the Construction of Micropatterned Biomimetic Membranes

“…[30][31][32] In the case of SPBs, the molecular packing within the bilayer is influenced by the substrate. 33,34 Both 1 and 2 showed distinctive polymerization behaviors, depending on the type of substrate. The comparison of two different types of amphiphiles, one being a single alkyl chain lipid and the other being a phopholipid with two alkyl chains, yielded valuable insight into some important aspects for the development of patterned biomimetic membranes based on the lithographic photopolymerization of bilayers.…”

Functional, Hierarchically Structured Poly(diacetylene)s via Supramolecular Self‐Assembly

“…[24][25][26][27][28][29] Secondly, topochemical diacetylene polymerizations are only possible if the monomers display crystalline order; they are strictly controlled by the crystal packing parameters and, as a result, highly regio-and stereospecific. [22,23] They have successfully been performed in (crystalline) self-assembled mono-or multi-layers of long-chain diynoic acid amphiphiles, [30][31][32][33][34] along 1D lamellar structures in selfassembled monolayers on surfaces; [35][36][37] or in vesicles and related tubular or helical superstructures formed by diacetylene containing lipid amphiphiles with chiral polar head groups such as phosphatidyl cholines, amino acids, or aldonamides. [38][39][40][41][42][43][44] However, only few examples of diacetylene polymerizations carried out in hydrogenbonded organogels and supramolecular polymers are known to date.…”