Effect of Chain Length Compatibility on Monolayers, Foams, and Macro- and Microemulsions

Sharma, Mahendra K.; Shiao, S. Y.; Bansal, Vinod; Shah, Dinesh O.

doi:10.1021/bk-1985-0272.ch007

Cited by 5 publications

(1 citation statement)

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“…The area per lecithin molecule was altered (in 5-Å 2 stages) over the range 50 to 75 Å 2 because the estimates in the literature for the minimal area per molecule of lecithin generally fall within this region (15,20,21). For the cosurfactants studied, a much larger area per molecule of 30 Å 2 was used because there is at least one report in the literature that short-chain alcohols, when present in a mismatched monolayer (ie shortchain alcohols in combination with longer chain molecules), exhibit a larger area per molecule because of thermal motions of the chain (22). Although log P was experimentally determined in the present study, its value was altered to see what effect it had on the results, with values of ±10% of the experimentally determined figure being used.…”

Section: Discussionmentioning

confidence: 99%

Particle size analysis of concentrated phospholipid microemulsions: I. Total intensity light scattering

2000

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Water-in-oil phospholipid microemulsions prepared from a constant total surfactant/cosurfactant concentration of 25 wt% at four different lecithin/alcohol weight ratios (K m of 1:1, 1.5:1, 1.77: 1, and 1.94:1) and containing water concentrations (or volume fractions) ranging from 2.0 to 26 wt% (or 0.04 to 0.26) have been examined at 298 K using total intensity light scattering. The data obtained were analysed using the hard-sphere model of Percus-Yevick, modified to account for the partitioning of the alcohol between the various phases. The light-scattering results showed that, regardless of the K m or the alcohol used, a minimum water concentration of at least 9 wt% was required for the formation of a microemulsion; although this value was reasonably constant for each of the alcohols investigated, there was a tendency for a slightly higher concentration of water to be required for microemulsion formation at higher K m values. Simple calculations suggested that a microemulsion was formed only when sufficient water was present to satisfy the hydration of both the phospholipid head groups and the hydroxyl groups of the cosurfactant associated with the droplet. At water concentrations lower than this minimum value, a cosolvent system was observed. In all systems above this minimum concentration, as the concentration of water increased, the size of the microemulsion droplets also increased. Surprisingly, however, there was little difference in the size of the microemulsion droplets obtained with the different alcohols, regardless of the K m , although for a particular alcohol there was some indication that the higher K m systems produced the slightly smaller droplets for an equivalent water

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Section: Discussionmentioning

confidence: 99%