Peroxy radicals as motional probes at the end of isolated polystyrene chains and on the cellulose surfaces in vacuum

• Published in: Cellulose (London) Vol. 23; no. 2; pp. 1123 - 1135
• Main Authors: Motokawa, Toshiyuki, Makino, Masakazu, Sakaguchi, Masato
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01-04-2016; Springer Nature B.V
• Subjects: Bioorganic Chemistry; Cellulose; Ceramics; Chain dynamics; Chain mobility; Chemistry; Chemistry and Materials Science; Composites; Crystalline cellulose; environmental factors; free radicals; Glass; Glass transition temperature; Molecular motion; Natural Materials; Organic Chemistry; Original Paper; Peroxy radicals; Physical Chemistry; Polymer Sciences; polymerization; Polystyrene resins; polystyrenes; roots; styrene; Sustainable Development; Temperature; Tumbling; Tumbling motion; Peroxy radical; Mechanochemical polymerization; Surface of cellulose; Isolated polystyrene chain; Motional probe; Cellulose
• ISSN: 0969-0239; 1572-882X
• DOI: 10.1007/s10570-016-0870-9

The isolated polystyrene chains spin-labeled with peroxide radical at the free end (IPSOO) in which the chain roots were covalently bonded to the surface of microcrystalline cellulose (MCC) powder were produced by mechanochemical polymerization of styrene initiated by MCC mechanoradicals. The IPSOO was used as motional probes at the ends of isolated polystyrene chains tethered on the surface of MCC powder. Two modes for the molecular motion of IPSOO were observed. One was a tumbling motion of IPSOO on the MCC surface, defined as a train state, and another was a free rotational motion of IPSOO protruding out from the MCC surface, defined as a tail state. The temperature of tumbling motion (T ₜᵤₘ) of IPSOO at the train state was at 90 K with anisotropic correlation times. T ₜᵤₘ (90 K) is extremely low compared to the glass transition temperature (T g ᵇ ; 373 K) of polystyrene in the bulk. At temperatures above 219 K, the IPSOO was protruded out from the MCC surface, and freely rotated at the tail state. The train–tail transition temperature (T ₜᵣₐᵢₙ–ₜₐᵢₗ) was estimated to be 222 K. T ₜᵤₘ (90 K) and T ₜᵣₐᵢₙ–ₜₐᵢₗ (222 K) are due to the extremely low chain segmental density of IPSOO on the MCC surface under vacuum. The interaction between IPSOO and the MCC surface is a minor contributing factor in the mobility of IPSOO on the surface under vacuum. It was found that peroxy radicals are useful probes to characterize the chain mobility reflecting their environmental conditions.