Formation of worm-like micelles from a polystyrene–polybutadiene–polystyrene block copolymer in ethyl acetate

Abstract

An investigation has been made of micelle formation by a polystyrene-polybutadienepolystyrene block copolymer in ethyl acetate, which is a selectively bad solvent for polybutadiene; the number-average molecular weights of the three blocks were 12900,66000 and 13 700, respectively. As the temperature was raised dilute solutions of the copolymer in ethyl acetate showed a distinct cloud-point, which moved to higher temperatures with increases in concentration. On raising the temperature further the solutions gradually became clear again.Light scattering and electron microscopy studies showed that the onset of cloudiness was due to the formation of long worm-like micelles from spherical micelles. The clearing of solutions at higher temperatures occurred because the micelles dissociated to form copolymer molecules in the free-chain form. The cores of both types of micelle were composed of swollen polybutadiene blocks and the outer fringes of the micelles of polystyrene blocks. The spherical micelles had a fairly narrow size distribution. The worm-like micelles had a wide distribution of contour lengths but possessed a narrow size distribution in the radial direction,A second polystyrene-polybutadiene-polystyrene copolymer having shorter blocks than the first copolymer showed a similar type of solution behaviour at lower temperaturs.

Investigations of a series of nonionic surfactants of sugar-lipid hybrids by light scattering and electron microscopy

“…The different techniques of electron microscopy are described in the appendix. At this point, the formation of worm-like and spherical miceIIes, which undergo association to larger aggregates, were also observed with block-copolymers [46][47][48]. The conditions under which rod-like or spherical micelles are observed with these macromolecules have not, to our knowledge, yet been systematically explored.…”

Poly[(2-ethylhexyl acrylate)-ran-(tert-butyl acrylate)]-block-poly(2-cinnamoyloxyethyl acrylate) synthesis and properties

“…Monomer tBA was distilled over CaH 2 . PMDETA, tol-d 8 , and diisopropylamine were distilled prior to use. MBP and 1-bromohexane were distilled under vacuum.…”

“…Copolymerization reactivity ratios r EXA and r tBA were determined in tol-d 8 The mixture was freed of oxygen by three freezeepumpe thaweAr filling cycles as described above for P(EXA-r-tBA)-Br synthesis before the flask was immersed in an oil bath preheated at 60 C. The polymerization was performed at this temperature for 26 h. After cooling to room temperature, the mixture was diluted with THF and filtered through a column of neutral alumina to remove the catalyst. The filtrate was concentrated by rota-evaporation and the polymer was precipitated by adding into a mixture of water and methanol at v/v ¼ 1/3.…”

Hydrodynamic studies on micellar solutions of styrene–butadiene block copolymers in selective solvents

“…The micelle formation in selective solvents (pure and mixed solvents) for each block has been studied using several techniques viz. light scattering (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14), viscosity (4,7,9,(13)(14)(15), osmometry (12,15,16), ultramicroscopy (1 9), electron microscopy (19)(20)(21), gel permeation chromatography (20), nmr (22,23), small angle X-ray scattering (17,18,24,25), photon correlation spectroscopy (19,26), and sedimentation measurements (10,15).…”