Abstract
Nanoblends, in which dispersed-phase domains exhibit length scales of order 100 nm or less, are made using a continuous, industrially scalable, mechanical process called solid-state shear pulverization (SSSP). An 80/20 wt% polystyrene (PS)/poly(methyl methacrylate) (PMMA) blend processed by SSSP and consolidated by platen pressing, without melt processing, exhibits a quasi-nanostructured morphology with many irregular, minor-phase domain sizes of ∼100 nm or less. After short-residence-time single-screw extrusion, the pulverized blend exhibits spherical dispersed-phase domains with a number-average diameter of 155 nm. Thus, SSSP followed by certain melt-processing operations can yield nanoblends. However, the pulverized blend exhibits significant coarsening of the dispersed-phase domains during long-term, high-temperature static annealing, indicating that SSSP followed by other melt processes may yield microstructured blends. In order to suppress coarsening, a styrene (S)/methyl methacrylate (MMA) gradient copolymer is synthesized by controlled radical polymerization. When 5 wt% S/MMA gradient copolymer is added to the PS/PMMA blend during SSSP, the resulting blend exhibits a nanostructure nearly identical to that of the blend without gradient copolymer, and coarsening is nearly totally suppressed during long-term, high-temperature static annealing. Thus, SSSP with gradient copolymer addition can yield compatibilized nanoblends. Morphologies obtained in the pulverized PS/PMMA nanoblend are compared with those in blends of PS/poly(n-butyl methacrylate) and PS/high-density polyethylene made using identical SSSP conditions, providing for commentary on the ability of SSSP to produce nanostructured blends as a function of blend components.
Original language | English (US) |
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Pages (from-to) | 6773-6781 |
Number of pages | 9 |
Journal | Polymer |
Volume | 47 |
Issue number | 19 |
DOIs | |
State | Published - Sep 7 2006 |
Funding
The support by Northwestern University, the NSF-MRSEC program (Grant DMR-0076096 and Grant DMR-0520513), and a 3M Fellowship (to JK) is gratefully acknowledged. We also acknowledge the use of field-emission and standard scanning electron microscopes in a shared user facility of the Northwestern University Materials Research Center. We also thank Prof. SonBinh Nguyen and Dr. Hongying Zhou for the synthesis of alkoxyamine 29 that was originally used in Refs. [53,55] .
Keywords
- Gradient copolymers
- Nanoblend
- Solid-state shear pulverization
ASJC Scopus subject areas
- Organic Chemistry
- Polymers and Plastics
- Materials Chemistry