No abstract

Particles of cross-linked polystyrene were prepared by suspension cross-linking of polystyrene dissolved in nitrobenzene at a constant initial concentration of 1.37 X 10"3 mol/cm3. The suspending medium was water containing poly(vinyl alcohol) at different concentrations varying from 0 to 5 X 10~4 g/cm3. The catalyst was ZnCI2 in a 70 wt % aqueous solution. Cross-linking was achieved by use of 1,4-dichloromethyl-2,5-dimethylbenzene (DCMDMB) which was dissolved in nitrobenzene at initial cross-linking ratios, X, of 0.0625, 0.125, 0.15, 0.33, 0.50, and 0.75 mol of DCMDMB/mol of polystyrene repeating unit. Reaction temperatures varied from 45 to 70 °C, reaction times were between 2 and 16 h, and agitation speed was controlled. Particle size distribution and equilibrium swelling behavior were determined as a function of experimental conditions. Spherical particles were obtained with number average particle size varying between 13 and 59 pm for critical point-dried particles and between 22 and 155 pm for chloroform-swollen particles. The average diameter of the particles decreased with increasing cross-linking ratio.

Crosslinked polystyrene particles were prepared by Friedel–Crafts suspension crosslinking of polystyrene using 2,4‐dichloromethyl‐2,5‐dimethyl benzene as crosslinking agent. The polymer was dissolved in nitrobenzene and reaction occurred in a 70 wt % aqueous solution of ZnCl2 with poly(vinyl alcohol) as a suspending agent. The spherical particles produced were swollen in toluene, chloroform, and tetrahydrofuran to determine their equilbrium polystyrene volume fraction. Analysis of the crosslinked macromolecular structure gave values of number‐average molecular weight between crosslinks of M̄c = 900–5900 increasing as the nominal crosslinking ratio X decreased from 0.75 to 0.0625 mol of crosslinking agent per mole of polystyrene repeating unit. Porosimetric analysis contributed to the understanding of the importance of the pore structure for swelling behavior.

Aus den Al‐alkoholaten (I) entstehen thermisch die Olefine (II), aus dem sekundären Carbinol (III) erhält man über das Alkoholat ein Gemisch aus den Isomeren (IIa) und (IV).