Phase separation and permeability in polyisobutylene-based miktoarm star polymers

Abstract

The phase behavior of (PS‐PIB)2‐s‐PAA miktoarm star terpolymers with varying volume fractions of PAA was investigated directly by transmission electron microscopy, atomic force microscopy, and small‐angle X‐ray scattering, and indirectly by thermogravimetric analysis and degree of water sorption. The microdomains of (PS‐PIB)2‐s‐PAA demonstrate a unique and unexpected progression from highly ordered cylinders, to lower ordered spheres, to gyroid structures with increasing PAA content from 6.6 to 47 wt %. Interestingly, the phase behavior in the miktoarm star polymer system is significantly different from that reported previously for the linear counterpart of similar composition (PAA‐PS‐PIB‐PS‐PAA), where a steady progression from cylindrical to lamellar morphology was observed with increasing PAA content. At low PAA concentrations, the morphology is driven primarily by the relative solubility of the components, while at high PAA content the molecular architecture dominates. Thermal annealing demonstrated the thermodynamic stability of the morphologies, indicating the potential for design of novel microstructures for specific applications through precise control of architecture, composition, and interaction parameters of the components. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 916–925

Effect of Molecular Asymmetry on the Formation of Asymmetric Nanostructures in ABC-Type Block Copolymers

“…In this work, we focus on the exploration of structures composed of different arrangements of minority A- and C-domains formed from asymmetric ABC-type block copolymers. We include not only compositional but also topological asymmetries into A- and C-blocks in order to expand the phase region of asymmetric morphologies composed of A- and C-domains in different sizes or even in different geometries and thus to obtain more different kinds of asymmetric morphologies, especially novel hybrid sphere-network morphologies. − Symmetric A- and C-cylinders are alternately arranged on a tetragonal array, and symmetric A- and C-spheres alternate on a BCC lattice. When and how does the asymmetry between A- and C-domains change their packing?…”

“…Hopefully, the additional asymmetry will facilitate the formation of asymmetric or hybrid structures. Note that the A­(BC) 2 miktoarm star copolymer has been synthesized by experiment. , Moreover, the self-assembly of A­(BC) m ( m = 2, 3, and 4) has been investigated using SCFT , and dissipative particle dynamics (DPD) simulations. , However, the previous work rarely focused on the exploration of novel hybrid morphologies as well as their formation mechanism.…”

Surface and interfacial segregation of polyethersulfone deuterated chain ends determined by neutron reflectivity

“…Functional OH chain ends of commercial PESU ( 6 ) were reacted with deuterated TNCO ( 5 ) and bSO 2 Cl ( 8 ) as shown in Schemes and , respectively. Prior to reaction, commercial PESU was fractionated into systems of controlled molecular weight and narrowed distribution via a fractional precipitation method outlined in a previous publication . The molecular weight, distribution, and polymer dimensions of the PESU fractions used in this study are summarized in Table .…”

“…Prior to reaction, commercial PESU was fractionated into systems of controlled molecular weight and narrowed distribution via a fractional precipitation method outlined in a previous publication. 11,17 The molecular weight, distribution, and polymer dimensions of the PESU fractions used in this study are summarized in Table 1. Fractions were chosen with M w similar to that of PDP-PESU1.…”