Design Of PS-PEO Block Copolymer And Its Application In Suspension Polymerization Of Styrene

Polyethylene oxide?PEO?has good hydrophilicity and the polymer dispersants including PEO block can be prepared by blocking,grafting or random copolymerization.The stability of adsorption lipophilic segment between particles and the suspension polymerization process can be improved effectively by controlling the ratio of lipophilic block of polymer dispersants.In this paper,the polystyrene-polyethylene oxide block copolymers?PS-b-PEO and PEO-b-PS-b-PEO?with controlled molecular structure parameters were synthesized by living anionic polymerization of styrene and ethylene oxide,n-BuLi and di-lithium as initiators,i-Bu₃Al as cocatalyst.The structures of the PS-PEO bolck copolymers were characterized by FT-IR,GPC,¹H-NMR and DSC.The PS-b-PEO and PEO-b-PS-b-PEO were tested by hanging-tab method,contact angle test,dispersion property,and retention property test to characterize the dispersing properties of them.Finally,PS-b-PEO and PEO-b-PS-b-PEO were respectively used as dispersants in the suspension polymerization of styrene and study the influence of the mass fraction of PEO block in polystyrene-ethylene oxide block copolymers,the amount of PS-PEO?PEO block content of styrene monomer mass fraction?,and the stirring rate to styrene suspension polymerization.Moreover,the dispersion effect difference of PS-b-PEO and PEO-b-PS-b-PEO block copolymers as dispersants was discussed.The results show that the PS-PEO with the mass average molecular weight of PS block5000 g/mol and the mass fraction of PEO block from 3%to 30%are successfully synthesized.As the mass fraction of the PEO block of PS-PEO increases,the crystallinity and the CMC value increases,the water contact angle,the dispersion ability and the gel-retaining ability decrease respectively.In the suspension polymerization of styrene by using PS-PEO as dispersants,when the amount of PS-PEO is the same,with the increase of mass fraction of PEO block,the particle size of PS particles obtained by suspension polymerization of styrene increases and the distribution becomes wider.When the polystyrene-ethylene oxide block copolymers with the mass fraction of PEO block being 5.0%were used as stabilizers,the particles size of polystyrene tends to increase and the particles size distribution tends to narrow as the amount of PS-PEO increases.The polymerization can still proceed stably by increasing the mechanical stirring speed,but the probability of coalescence increases,the particle size and uniformity of the particles change significantly.PS-b-PEO and PEO-b-PS-b-PEO were significantly different as dispersants.The PS particles obtained by using PEO-b-PS-b-PEO as dispersants were spherical;the PS particles obtained by PS-b-PEO as dispersants were spindle-shaped.PEO-b-PS-b-PEO with the same mass of components has better dispersion effect than PS-b-PEO as a dispersant.