From brush to dendritic structure: Tool for tunable interfacial compatibility between the iron-based particles and silicone oil in magnetorheological fluids

Comprehensive magnetic particle stability together with compatibility between them and liquid medium (silicone oil) is still a crucial issue in the case of magnetorheological (MR) suspensions to guarantee their overall stability and MR performance. Therefore, this study is aimed at improving the interfacial stability between the carbonyl iron (CI) particles and silicone oil. In this respect, the particles were modified with polymer brushes and dendritic structures of poly(2-(trimethylsilyloxy)ethyl methacrylate) (PHEMATMS), called CI-brushes or CI-dendrites, respectively, and their stability properties (corrosion, thermo-oxidation, and sedimentation) were compared to neat CI ones. Compatibility of the obtained particles and silicone oil was investigated using contact angle and off-state viscosity investigation. Finally, the magneto-responsive capabilities in terms of yield stress and reproducibility of the MR phenomenon were thoroughly investigated. It was found that MR suspensions based on CI-brushes had significantly improved compatibility properties than those of neat CI ones; however, the CI-dendrites-based suspension possessed the best capabilities, while the MR performance was negligibly suppressed.Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT, (RP/CPS/2022/003); Grantová Agentura České Republiky, GA ČR, (23-07244S); Narodowa Agencja Wymiany Akademickiej, NAWA, (PPM/ULM/2019/1/00102

Polyacrylamide brushes with varied morphologies as a tool for control of the intermolecular interactions within EPDM/MVQ blends

The specific interactions between polyacrylamide brushes composed of polyacrylamide chains tethered to montmorillonite particles (Mt-g-PAm) and the individual components of immiscible ethylene-propylene-diene modified with sorbic acid (EPDM) and methyl vinyl silicone (MVQ) blends were studied. The effect of various lengths of PAm chains and their grafting density on montmorillonite (Mt) surface was investigated. It was determined that, due to interactions generated within the system through carboxyl and amide groups the brush particles were selectively located at the EPDM/MVQ interphase and in the EPDM phase. Furthermore, the longer PAm chains resulted in an increase of the glass transition of EPDM, unification of blend morphology, and the reduction of crystallinity of the MVQ phase. Therefore, precisely designed polymer brushes could be considered as novel functional compatibilizers, that provide a new tool for the future material designing. © 2021 Elsevier LtdNational Science Centre, PolandNational Science Center, PolandNational Science Centre, Poland [UMO-2016/23/P/ST5/02131]; European UnionEuropean Commission [665778]; Ministry of Education, Youth and Sports of the Czech republic -DKRVO [RP/CPS/2020/003]; Research & Innovation Operational Programme - ERDF [313021T081]; [VEGA 2/0129/19]; [APVV-19-0338]665778; UMO-2016/23/P/ST5/02131; Slovenská Akadémia Vied, SAV: 313021T081; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT: RP/CPS/2020/003; Narodowe Centrum Nauki, NCN; European Regional Development Fund, FEDER: APVV-19-0338, VEGA 2/0129/1

One-pot strategy for the preparation of electrically conductive composites using simultaneous reduction and grafting of graphene oxide via atom transfer radical olymerization

In this work, a facile "one-pot"approach for the preparation of composites with tunable electrical conductivity and viscoelastic properties is presented. The effect of reaction conditions, such as reaction time and temperature as well as the structure and concentration of the tertiary amine used as a component of the catalytic complex, on the reduction of graphene oxide was investigated. The reaction conditions were optimized for the simultaneous GO reduction during the synthesis of two types of polymers, poly(methyl methacrylate) (PMMA) and poly(styrene-co-acrylonitrile) (SAN). GO-graft-poly(methyl methacrylate) (GO-g-PMMA) and GO-graft-poly(styrene-co-acrylonitrile) (GO-g-SAN) hybrids with electrical conductivity ranging from 10-8 to 100 S cm-1 were prepared using selected tertiary amine-based ligands. Finally, the reaction conditions were adapted for the in situ preparation of GO-g-PMMA/PMMA and GO-g-SAN/SAN composites with electrical conductivity ranging from 10-14 to 10-4 S cm-1. The mechanical properties of the synthesized composites were compared with composites prepared from GO and commercial PMMA or SAN. © 2021 American Chemical Society.RP/CPS/2020/003; UMO-2016/23/P/ST5/02131; Horizon 2020 Framework Programme, H2020: 665778; Slovenská Akadémia Vied, SAV: 313021T081; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT; Narodowym Centrum Nauki, NCN; Vedecká Grantová Agentúra MŠVVaŠ SR a SAV, VEGA: 2/0129/19, APVV-19-0338; European Regional Development Fund, ERDFNational Science Centre, Poland through POLONEZ from the European Union's Horizon 2020 research and innovation program under Marie Sklodowska-Curie grant [UMO-2016/23/P/ST5/02131, 665778]; Ministry of Education, Youth and Sports of the Czech Republic-DKRVO [RP/CPS/2020/003]; Research & Innovation Operational Program - ERDF [313021T081]; VEGAVedecka grantova agentura MSVVaS SR a SAV (VEGA)European Commission [2/0129/19]; [APVV-19-0338

Influence of PMMA brushes grafted from GO on rheological properties of PMMA/SAN immiscible blend in shear and elongation flow

In real technological processes, both shear and elongational flow is present. The material properties may differ significantly under both types of flow. Hence, they both define the final morphology and thus properties of the materials. In this work, the morphology of immiscible blends containing polymer hybrid particles was related to extensional rheological properties for the first time. The effect of various lengths of polymer brushes grafted from graphene oxide particles (GO) surface was investigated. As a polymer matrix the immiscible blend of poly(methyl methacrylate)/styrene-co-acrylonitrile (PMMA/SAN) was used. Thus the poly(methyl methacrylate) (PMMA) brushes grafted from GO (GO-g-PMMA) with various number average molar masses (Mn) of PMMA brushes with respect to chain entanglement limit of freely dispersed PMMA were prepared. The extensional rheological properties were affected by Mn of PMMA brushes, while the rheological properties in shear were unchanged. Transmission electron microscopy revealed the compatibilization effect for short densely grafted brushes with Mn of 10,300 g/mol, as smaller domains were observed. On the contrary, the higher Mn PMMA brushes facilitated coalescence. With increasing length of brushes, the elongational viscosity at low elongation rates (∼ 0.1 s−1) was not sufficient enough to cause fiber breakup and thus elongated domains were formed.665778; Slovenská Akadémia Vied, SAV: 313021T081; Ministerstvo Školství, Mládeže a Tělovýchovy, MŠMT: RP/CPS/2022/003; Narodowe Centrum Nauki, NCN: UMO-2016/23/P/ST5/02131; Vedecká Grantová Agentúra MŠVVaŠ SR a SAV, VEGA: 2/0137/23; European Regional Development Fund, ERDF: APVV-19-0338National Science Centre, Poland [UMO-2016/23/P/ST5/02131]; European Union [665778]; Ministry of Education, Youth and Sports of the Czech republic-DKRVO [RP/CPS/2022/003]; Integrated Infrastructure Operational Program - ERDF [313021T081]; [APVV-19-0338]; [VEGA 2/0137/23