Thermoplastic elastomers based on well-defined 10- and 20 arm star-like block copolymers containing middle soft poly(n-butyl acrylate) (PBA) block and outer hard poly(alpha-methylene-gamma-butyrolactone) (PMBL) block were synthesized by atom transfer radical polymerization (ATRP). Phase separated cylindrical or lamellar morphologies, depending on the copolymers composition and the annealing temperature of the films, were observed by atomic force microcopy and small-angle X-ray scattering. The mechanical and thermal properties of the copolymers were thoroughly characterized. The prepared copolymers retained their phase separated morphology even at temperatures exceeding 300 degrees C. Both tensile strength and elongation values for the star-like copolymers were considerably higher than for linear copolymers with similar composition. (C) 2010 Elsevier Ltd. All rights reserved.
Facile, Solution-Based Synthesis of Soft, Nanoscale Janus Particles with Tunable Janus Balance
作者:André H. Gröschel、Andreas Walther、Tina I. Löbling、Joachim Schmelz、Andreas Hanisch、Holger Schmalz、Axel H. E. Müller
DOI:10.1021/ja305903u
日期:2012.8.22
We present a novel, versatile, and simple solution-based routine to produce soft, nanosized Janus particles with tunable structural and physical properties at high volume yield. This process is based on the cross-linking of compartments within precisely defined multicompartment micelles (MCMs), which are themselves formed by the self-assembly of ABC triblock terpolymers. Therein, the C blocks form the stabilizing corona emanating from B compartments, which in turn reside on an A core. Cross-linking of the B compartments allows to permanently fixate the phase separated state and dissolution in a good solvent for all blocks breaks up the MCMs into single Janus particles They now consist of a core of cross linked B blocks and two phase separated hemispheres of A and C. The process gives access to unprecedented structural features such as tunable core diameter and control over the Janus balance ranging from dominant A side to equal hemispheres to dominant C side. We demonstrate that this simple one pot approach can be extended to a range of triblock terpolymers with different block lengths and block. chemistries to furnish a library of tailor-made Janus particles with widely tunable physical properties. Such a diversity and simplicity has remained unreachable with our previously developed approach using the controlled cross-linking of bulk morphologies. We show that this new synthetic route can be upscaled to a high volume yield of 10 wt %, thereby enabling large-scale applications. We further demonstrate the effect of the Janus balance on colloidal self-assembly. Janus particles with a dominant hydrophobic and a small hydrophilic patch aggregate into large clusters in water, but merely di- or trimerize in chloroform.
Synthesis, Characterization, and Properties of Starlike Poly(<i>n</i>-butyl acrylate)-<i>b</i>-poly(methyl methacrylate) Block Copolymers
subsequently esterified. Partial star coupling during the star extension with PMMA blocks was observed, and the coupling increased with increasing number of arms and arm length. Phase-separated morphologies of cylindrical hard PMMA block domains arranged in the soft PBA matrix were observed by atomic force microscopy and small-angle X-ray scattering. The mechanical and thermalproperties of the copolymers were