Colorimetric mechanophores, which change color through force-induced covalent bond breakage, have been incorporated into polymer chains to create mechanochromic materials. However, the color change of most mechanophores is a turn-on response. In this work, we designed and synthesized a novel mechanoluminescent polymer system, PBA-SP-P(MMA-co-NBD), based on fluorescence resonance energy transfer (FRET) with spiropyran (SP) as a force-activated "on/off" mechanophore acceptor and nitrobenzoxadiazole (NBD) as a fluorescent donor. It is a comb polymer having NBD-bearing poly(methyl methacrylate) (PMMA) side chains grafted onto a poly(butyl acrylate) (PBA) backbone through SP groups. The processed polymer yields a morphology having NBD-containing PMMA nanodomains embedded into a PBA matrix with SP at the interface. The distance between NBD and SP functionalities is less than 10 nm with confinement of the nanophase separation, which effectively facilitates their fluorescence resonance energy transfer. Under uniaxial stretch, the materials change color at strains as low as about 18% and undergo a green-to-red fluorescence color switch. The two colors are ratiometric, exhibiting a linear correlation with strain after the onset of mechanoactivation. The color change is greatly enhanced right after failure. The fluorescence emission performance can be well controlled through regulating the PMMA/PBA and SP/NBD ratios in the synthesis. The synthesized polymer system exhibits a good potential as an indicator in monitoring microscale cut damages.
A novel bacterial strain, NH131 T , was isolated from deep-sea sediment of South China Sea. Cells were strictly aerobic, Gram-stain negative, short rod-shaped and motile with a single lateral flagellum. Strain NH131 T grew optimally at pH 6.5-7.0 and 25-30 6C. 16S rRNA gene sequence analysis revealed that strain NH131 T belonged to the genus Devosia, sharing the highest sequence similarity with the type strain, Devosia geojensis BD-c194 T (96.2 %). The predominant fatty acids were C 18 : 1 v7c, 11-methyl C 18 : 1 v7c, C 18 : 0 and C 16 : 0 . Ubiquinone 10 was the predominant ubiquinone. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phospholipid, three glycolipids and two unknown lipids. The DNA G+C content of strain NH131 T was 63.0 mol%. On the basis of the results of polyphasic identification, it is suggested that strain NH131 T represents a novel species of the genus Devosia for which the name Devosia pacifica sp. nov. is proposed. The type strain is NH131 T (5JCM 19305 T 5KCTC 32437 T ).The genus Devosia was first described by Nakagawa et al. (1996) as a result of the reclassification of 'Pseudomonas riboflavina' (Foster, 1944). The genus accommodates Gramstain negative, rod-shaped, aerobic, oxidase-positive bacteria containing ubiquinone 10 (Q-10) or Q-11 as the predominant respiratory quinone. The DNA G+C contents of bacteria of the genus Devosia range from 59.5 to 66.2 mol% (Yoon et al., 2007). At the time of writing, the genus Devosia comprises 15 species with validly published names, which can be found in the LPSN (Parte, 2014), and the species 'Devosia lucknowensis' (Dua et al., 2013) with a non-validly published name. In our attempts to study bacterial diversity of deep-sea sediments in the South China Sea, the marine strain NH131 T was isolated. In this paper, the classification of strain NH131 T by a polyphasic approach based on physiological, chemotaxonomic and phylogenetic analyses is described.Strain NH131 T was isolated from deep-sea sediment in the South China Sea. The sample of sediment was diluted with a tenfold dilution series method, spread on medium 702 (Nakagawa et al., 1996), which contained (per litre) 10.0 g peptone, 2.0 g yeast extract, 1.0 g MgSO 4 . 7H 2 O and 15 g agar (if needed) (pH 7.0), and incubated at 28 u C. After 3 days of aerobic incubation, one white colony, designated NH131 T , was picked. The colony was slightly convex, shiny and ranged from 0.5 to 1.0 mm in diameter with a complete rim.Cell morphology was examined by optical (BX40, Olympus) and transmission electron (JEM-1230, JEOL) microscopy using exponentially growing cells which were incubated in medium 702 for 24 h. The temperature range for growth of strain NH131 T was investigated on medium 702 at different temperatures (5-50 u C, in 5 u C increments) and the pH range was determined by adjusting the medium to pH 5.0-10.0 (in increments of 0.5 pH units) (Gomori, 1955). Growth under anaerobic conditions was determined after incubation of the novel strain in an anaerobic chamber on trypt...
Colorimetric mechanophores like spiropyran (SP) represent an emerging type of interesting signal molecule that can be incorporated into polymers or other materials as a stress transducer. In this work, a new type of spiropyran‐containing inimer molecule MA‐SP‐Br are designed and synthesized, which is incorporated into polybutylacrylate (PBA) chains through reversible addition‐fragmentation chain transfer (RAFT) copolymerization with n‐butyl acrylate (BA). PBA‐SP‐Br is then used as a macro‐initiator to graft polystyrene (PS) side chains from the PBA backbone through atom transfer radical polymerization (ATRP) of styrene. The resulting comb‐structured graft copolymer PBA‐SP‐PS contains 0.15–0.34% SP and exhibits a characteristic feature of thermoplastic elastomers. Under uniaxial stretch, the materials possess an excellent mechano‐responsivity and change color at strains as low as about 14%.
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