Structural Investigation of Micelles Formed by an Amphiphilic PEP−PEO Block Copolymer in Water

Abstract

Micelles of a poly(ethylene-co-propylene)-block-Poly(ethylene oxide) (PEP−PEO) copolymer in water were investigated by small angle neutron scattering (SANS), dynamic light scattering (DLS), and viscometry. The block copolymer was built of a partially deuterated PEP block and a hydrogeneous PEO block with an overall molecular weight of 11.1 × 103. The SANS measurements were performed at four contrasts in order to get detailed structural information about the micellar aggregates. The different scattering curves could be described very well by a spherical core−shell model with constant density in both parts. The sharp edges of the polymer density distribution were smeared by multiplication with a Gaussian in Q-space. The model yielded a core radius of R C = 176 Å and an overall micellar radius of R M = 294 Å. The smearing ranges were 11 and 32 Å, respectively. The fit further yielded an aggregation number of P = 2430. DLS measurements reveal a narrow monomodal distribution of relaxation frequencies, indicating the existence of only one aggregated species. The obtained hydrodynamic radius, R H = 339 Å, as well as the radius determined by viscosity measurements, R V = 324 Å, are consistent with the result of the model fitting. The unusually large aggregation number could be explained by the large interfacial tension between water and PEP in terms of simple thermodynamic models.

Surfactant or block copolymer micelles? Structural properties of a series of well-defined n-alkyl–PEO micelles in water studied by SANS

“…13,[27][28][29] Contrary to many other techniques, SAXS/SANS provide quantitative information of the detailed shape and size of nanostructures in solution. In addition, SANS provides additional advantages in terms of contrast variation through relatively simple hydrogen/ deuterium substitution that allows the different parts of the micelles (core, shell) to be selectively highlighted.…”

“…Moreover, the control of the synthesis allowed us to accurately vary both the length of the n-alkyl group and the PEO block beyond that for Brij surfactants which are generally only available with C 12 or C 18 hydrophobic blocks and rather short PEO segments. By a careful quantitative analysis of the SANS data with a core-shell model, we analysed the micellar structure for a series of C n -PEO5 polymers with n ranging from 18 to 30 and for C 27 with three further PEO molecular weights of 10 kg mol À1 , 20 kg mol À1 and 40 kg mol À1 . In addition from previous work we know that the system is able to attain equilibrium since molecular exchange is active for all n-alkyl-PEO micelles.…”

Development of Novel Cosmetic Base Using Sterol Surfactant. I. Preparation of Novel Emulsified Particles with Sterol Surfactant+

“…glyceryl tri(2-ethylhexanoate) and di(2-ethylhexyl) succinate) and water. On the other hand, because EPDME is a random copolymer and differs from a block copolymer that cam make micelle structure in water [12][13][14][15][16] , EPDME is unable to form self-assemble structure by itself.…”

Ultrasoft Colloid-Polymer Mixtures: Structure and Phase Diagram

“…Partially deuterated PEP-PEO block polymers and partially deuterated PEO chains were synthesized by anionic [20]. Molecular details of the systems are given in ].…”