Polymerized surfactant vesicles. Determinations of rates and degrees of polymerization in vesicles prepared from styrene-containing surfactants

Abstract

Rate constants ( q / E values) for laser pulse initiated photopolymerization have been determined for 1200-2700-&diameter bilayer surfactant vesicles prepared from dioctadecylmethyl(2-[ (4-vinylbenzoy1)-oxylethy1)ammonium bromide (31, from mixtures of dioctadecyldimethylammonium bromide (DODAB) and vinylbenzoic acid, from mixtures of 3 and DODAB, and from mixtures of 3 and vinylbenzoic acid. q / E values were 1.35 J-' for 1650-A-diameter 3 vesicles, were 0.059 J-' for mixed vesicles prepared from vinylbenzoic acid and DODAB (0.25:l mole fraction), varied between 0.123 and 1.46 J-' for vesicles prepared from different mixtures of DODAB and 3, and varied between 0.16 and 0.314 J-l for different mixtures of vinylbenzoic acid and DODAB. Plots of polymerization rate constants against the mole fraction of 3 in vesicles prepared by cosonicating 3 + DODAB were found to increase curvilinearly to a plateau value, indicating domain formation. Subsequent to vesicle polymerizations, cumulants, weight-and number-average molecular weights of the separated poly(viny1benzoates) and, hence, the average chain lengths were determined by gel exclusion chromatography. The average chain lengths varied from 10 in laser-polymerized 3 vesicles, through 20 in laser-polymerized vesicles prepared from mixtures of DODAB and vinylbenzoic acid, to 40 in laser-polymerized vesicles prepared from mixtures of 3 and vinylbenzoic acid. These relatively small chain lengths were discussed in terms of the restricted geometries prevailing a t intravesicular surface polymerizations. Fluorescence measurements and a Monte Carlo based computer simulation of the photopolymerization were used to substantiate the proposed mechanism of vesicle polymerization.

Solid Vesicle Membrane Made of meso-Tetrakis[(bixinylamino)-o-phenyl]porphyrins

“…It may be considered as a single, balloon-shaped polymer molecule. In the case of other polymerized lipid vesicular membranes, vesicle curvature generally prevents formation of extended polymers originated from ene or diyne monomers. − Only central vinyl groups connecting both ends of a bilayer membrane lead to very high molecular weights. 16a,c,20b Such cross-linked bilayers do, however, not survive 95% ethanol. In our case, there are so many polymerizable double bonds almost over the whole width of the monolayered membrane that the vesicle curvature can be retained if covalent bonds are formed at very different membrane sites.…”

Photopolymerization of two-component monolayers: mixtures of bis[2-(n-hexadecanoyloxy)ethyl]methyl(4-vinylbenzyl) ammonium chloride and dioctadecyldimethylammonium bromide

“…Evaluation of the excess free energy of interaction at a given surface pressure, µ, provides a more quantitative description of the mixing of the surfactants in the monolayer.26,26,33"36 As was shown, 1 and 5 are miscible and behave ideally in the limit of zero pressure; then ,8 = C ( 5 --5 6) dll Plots of AGaa vs mole fraction of 1 in 1 + 5 at 50 ( ), 40 ( ), 30 (*), 20 (•), and 10 (O) mN/m. where 5 , and 15 are the areas per molecule at pressure for pure components 1 and 5 and for the mixture, respectively.…”

“…The PPM model describes the photopolymerization of monolayers prepared from mixtures of 1 and 5 by equations [16][17][18][19][20]38 M-^RX (16) kp Rx + M -* R2 (17a…”

“…The same rate constant kp is written for each propagation step, assuming that the radical reactivity is independent of the chain length. The propagation of the radicals is terminated by Rm + Rn Pm+n (18) Rm + R,l -^P m + Pn (19) R" + X -* P" (20) The photopolymerization of monolayers prepared from mixtures of 1 and 5 (eq 16-20) is governed by the kinetic equations (eq [21][22][23][24][25][26]. (24) n=l Summing the infinite number of equations in dfi./dt, eq 25 and 26 describe the concentration changes of M and R during the photopolymerizations.…”

“…Figure 4.Plots of AGaa vs mole fraction of 1 in 1 + 5 at 50 ( ), 40 ( ),30 (*),20 (•), and 10 (O) mN/m.…”