Polymeric nanospheres [1,2] were formed in water from comb-like amphiphilic block copolymers (poly[ethylene oxide]-block-poly[octadecyl methacrylate]) (PEO-b-PODMA) and the internal morphology was determined through 3-dimensional cryo-electron tomographic analysis. Variation of polymer molecular weight and hydrophilic block weight content allowed for fine control over the morphology and the nanosphere internal structure; varying the solvent to water ratio used in their preparation allowed for control over nanosphere diameters. Construction of a phase diagram allowed us to determine the criteria for bicontinuous polymer nanosphere (BPN) formation namely from copolymers with molecular weights of up to 17 kDa and hydrophilic weight fractions of ≤ 0.25. BPNs were formed with solids content of 0.1 to 4 wt% and diameters from 70 to 460 nm. Significantly, altering the hydrophilic-hydrophobic balance within the block copolymer enabled control of the internal pore diameter of the BPNs, with diameters from 10 to 19 nm observed. PEO-b-PODMA BPNs undergo a phase transition from the ordered microphase separated bicontinuous morphology to a disordered nanophase separated morphology above 20oC. By incorporating a poly(docosyl methacrylate) (PDOMA) block in place of the PODMA the transition temperature was raised to above 40oC. Mixing varying wgt%s of ODMA and DOMA monomers in the hydrophobic block enabled tuning of the phase transition between 20oC and 40oC. Such temperature responsive nanospheres have obvious potential in controlled release applications. [3] [1] A. L. Parry, P.l H. H. Bomans, S. J. Holder, N. A. J. M. Sommerdijk, Stefano C. G. Biagini, Angew. Chemie Int. Ed. 2008, 47, 8859. [2] B. E. McKenzie, F. Nudelman, P. H. H. Bomans, S. J. Holder and N. Sommerdijk, J. .Amer. Chem.Soc., 2010, 132, 10256. [2] S.J. Holder, G. Woodward, B. McKenzie and N. A. J. M. Sommerdijk, RSC Advances, 2014, 4, 26354.

Constructing bicontinuous polymeric nanospheres from amphiphilic block copolymers: Control of pore size and thermal phase transitions

249th National Meeting (2015)

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