Switchable polymers

The covalent connection of two tetra-urea calix[4]arenes via their narrow rims leads to molecules which are bifunctional with respect to their ability to form dimeric capsules. This was used by Rebek and Castellano to form self-assembled polycaps , including also alternating structures based on the heterodimerization of aryl- and tosylureas [42,63]. The idea was later extended to switchable polymers [64]. We were recently able to show that the covalent connection of two tetra-urea calix[4]arenes via a rigid spacer between urea functions also leads to molecules 24, which can form polymeric assemblies (Scheme 5.22) [57,65]. 

Vohra, V. R., Schmidt, D. R, Ober, G. K., and Giannelis, E. P. 2003. Deinteicalation of a chemically switchable polymer from a layered silicate nanocomposite. Journal of Polymer Science, Part B ... 

Akai Y, Yamamoto T, Nagata Y, Ohmura T, Suginome M (2012) Enhanced catalyst activity and enantioselectivity wifli chirality-switchable polymer ligand PQXphos in Pd-catalyzed asymmetric silaborative cleavage of meso-methylenecyclopropanes. J Am Chem Soc 134(27) 11092-11095. doi 10.1021/ja303506k... 

Snndaram, H. S., Ella-Menye, J.-R., Brault, N. D., Shao, Q., Jiang, S. (2014). Reversibly switchable polymer with cationic/zwitterionic/anionic behavior through synergistic protonation and deprotonation. Chemical Science, 5, 200-205. 

Switchable polymer coatings can be prepared on a wide variety of biomaterials. To implement a particular switching effect, a stimuli-responsive layer is attached to the surface. Its molecular structure introduces the desired physicochemical mechanism, hi case of copolymers (also polymer blends, mixed brushes, etc.), the stimuli-responsive unit can be combined with a second unit that allows to set other material properties in a particular way. 

Le, X. T., P. Viel, P. Jegou, A. Sorin, S. Palacin. Electrochemical-switchable polymer film An emerging technique for treatment of metallic ion aqueous waste. Sep. Purif. Technol. 69, 2009 135-140. 

His research interests are in the domains of fire retardant, photo-crosslinkable, liquid crystalline polymers, LC thermosets, polymer-metal complexes, optical data storage, and photo and electrically switchable polymers. 

Using PGMA as an anchoring interlayer a switchable polymer nanolayer on the surface of PET textile material has been synthesized. The PET fabric changed the surface properties after being treated with different solvents (Fig. 17.11). When the fabric was exposed to toluene, it became hydrophobic and water did not penetrate the material. Conversely, water penetrated throughout the textile materials, if they were exposed to MEK. The wettability changes were reversible. 

See, for example, Marshall, K. L., E. Kimball, S. Mcnamara, T. Z. Kosc, A. Trajkovska-Petkoska, and S. D. Jacobs. 2004. Electro-optical behaviour of polymer cholesteric liquid crystal flake/fluid suspensions in a microencapsulated matrix, in Liquid Crystals VIII, edited by 1. C. Khoo, SPIE Proceedings Vol. 5518 (SPIE Bellingham, WA 2004) pp. 170-181 and references therein see also, Marshall, K. L., T. Z. Kosc, S. D. Jacobs, S. M. Paris, and L. Li. 2003. Electrically switchable polymer liquid crystal and polymer birefringent flake/fluid host systems and optical devices utilizing same, U.S. Patent No. 6,665,042 B1 (Dec 2003). 

Stimuli-responsive materials have attracted enormous interest in the fields of polymer, supramolecular, and colloidal science over the last few decades [1-5]. It can be anticipated that stimuli-sensitive systems in general and switchable polymers in particular will continue to be a thriving branch of chemistry. New applications can be envisioned, for instance, for controlled uptake and release, fine-tuning of mechanical properties, or actuating purposes. 

Here, we will consider changes in the accessibility of electrodes to electroactive substances by switchable polymer films, which are not directly redox-sensitive. A gating of hexacyanoferrates could be modulated by the presence of cholesterol, which complexes the collapsed poly(vinyl pyridine) matrix (hydrophobic at the pH used) [425]. The preparation of this membrane leads to pores that are filled upon complexation with cholesterol. At the same time, the accessibility of the electrode... 

Kumar S, Tong X, Dory YL, Lepage M, Zhao Y (2013) A C02-switchable polymer brush for reversible capture and release of proteins. Chem Commun 49(l) 90-92... 

Figure 4.38 Asymmetric hydrosilylation using chirality-switchable polymer adopting (a) P helical form or (b) M helical form.

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