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Chen Z, Seong HG, Hu M, Gan X, Ribbe AE, Ju J, Wang H, Doucet M, Emrick T, Russell TP. Janus bottlebrush compatibilizers. SOFT MATTER 2024; 20:1554-1564. [PMID: 38270211 DOI: 10.1039/d3sm01484c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2024]
Abstract
Bottlebrush random copolymers (BRCPs), consisting of a random distribution of two homopolymer chains along a backbone, can segregate to the interface between two immiscible homopolymers. BRCPs undergo a reconfiguration, where each block segregates to one of the homopolymer phases, adopting a Janus-type structure, reducing the interfacial tension and promoting adhesion between the two homopolymers, thereby serving as a Janus bottlebrush copolymer (JBCP) compatibilizer. We synthesized a series of JBCPs by copolymerizing deuterated or hydrogenated polystyrene (DPS/PS) and poly(tert-butyl acrylate) (PtBA) macromonomers using ruthenium benzylidene-initiated ring-opening metathesis polymerization (ROMP). Subsequent acid-catalyzed hydrolysis converted the PtBA brushes to poly(acrylic acid) (PAA). The JBCPs were then placed at the interface between DPS/PS homopolymers and poly(2-vinyl pyridine) (P2VP) homopolymers, where the degree of polymerization of the backbone (NBB) and the grafting density (GD) of the JBCPs were varied. Neutron reflectivity (NR) was used to determine the interfacial width and segmental density distributions (including PS homopolymer, PS block, PAA block and P2VP homopolymer) across the polymer-polymer interface. Our findings indicate that the star-like JBCP with NBB = 6 produces the largest interfacial broadening. Increasing NBB to 100 (rod-like shape) and 250 (worm-like shape) reduced the interfacial broadening due to a decrease in the interactions between blocks and homopolymers by stretching of blocks. Decreasing the GD from 100% to 80% at NBB = 100 caused an increase the interfacial width, yet further decreasing the GD to 50% and 20% reduced the interfacial width, as 80% of GD may efficiently increase the flexibility of blocks and promote interactions between homopolymers, while maintaining relatively high number of blocks attached to one molecule. The interfacial conformation of JBCPs was further translated into compatibilization efficiency. Thin film morphology studies showed that only the lower NBB values (NBB = 6 and NBB = 24) and the 80% GD of NBB = 100 had bicontinuous morphologies, due to a sufficient binding energy that arrested phase separation, supported by mechanical testing using asymmetric double cantilever beam (ADCB) tests. These provide fundamental insights into the assembly behavior of JBCPs compatibilizers at homopolymer interfaces, opening strategies for the design of new BCP compatibilizers.
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Affiliation(s)
- Zhan Chen
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
| | - Hong-Gyu Seong
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
| | - Mingqiu Hu
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
| | - Xuchen Gan
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
| | - Alexander E Ribbe
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
| | - Jaechul Ju
- Department of Chemistry, The University of Texas at Austin, Austin, TX, 78712, USA
| | - Hanyu Wang
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Mathieu Doucet
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
| | - Todd Emrick
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
| | - Thomas P Russell
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, MA, 01003, USA.
- Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 37831, USA
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