In the "cycloketyl radical mediated living polymerization"(CMP) process, a cycloketyl compound, [9,9′]bixanthenyl-9,9′ diol(BIXAN) was ultilized as initiator and mediator. The cycloketyl(CK) radical was used as the dormant radical to achieve the increase of molecular weight. Herein, a series of cycloketyl thioketones were synthesised by Lawesson's reagent by one step reaction with high yeild,and we found that, when a special cycloketyl thioketone compound, thioxanthene-9-thione(TXT), was added to a routine radical polymerization system, TXT could capture chain radical, and simultaneously formed an radical analogous to CK radical in structure,which could trigger the growth of polymer chains. This simple system was efficient to initiate the polymerization of methyl methacrylate(MMA) and in all cases the molecular weights increased with the increase of conversions. By the end-group analysis with 1 H-NMR and MALDI-TOF MS, it was confirmed that the P-STXT radical was used to control the polymerization. The re-initiating reactions were achieved when PMMA was used as the macro-initiator.
Xu YanGuan WangLi-Hua ZhangLi WangXiao-Fei LiuWan-Tai Yang
Co-immobilization of enzymes and microorganism is an effective way to enable cells to use nonmetabolizable substrates and accelerate reaction rate of overall process. Herein, a facile strategy to separately co-immobilize β-glucosidase(BG) and yeast cells on non-woven fabrics was developed. The BG was firstly in situ entrapped into poly(ethylene glycol)(PEG) network grafted on non-woven fabrics by visible light induced living/controlled graft polymerization. Then re-graft polymerization was performed on the as-formed BG loaded layer by taking advantage of living-grafting polymerization on its surface to in situ encapsulate yeast cells into the second PEG network layer. This layered structure of co-immobilization avoided possible interference between enzyme and cells. Viability assay of yeast cells demonstrated that most of cells were viable after immobilization. While immobilized BG showed decreased V_(max) compared to free BG, indicating that entrapping BG into inner PEG network layer restricted its accessibility with substrates. This co-immobilization sheet could successfully convert cellobiose to ethanol and a maximum of 98.6% bioethanol yield can be obtained after 48 h of simultaneous saccharification and fermentation(SSF). The co-immobilization sheet showed excellent reusability and could still reach more than 60% of original ethanol yield after reusing for 7 batches. Compared with the mixed co-immobilization, the sequential layered immobilization in this system showed better stability and higher ethanol yield.
An efective,value-added use of the large amounts of olefnic compounds produced in the processing of petroleum,aside from ethylene and propylene,has been a long outstanding challenge.Here,we developed a novel heterogeneous polymerization method,beyond emulsion/dispersion/suspension,termed self-stabilized precipitation(2SP)polymerization,which involves the nucleation and growth of nanoparticles(NPs)of a well-defned size without the use of any stabilizers and multifunctional monomers(crosslinker).Tis technique leads to two revolutionary advances:(1)the generation of functional copolymer particles from single olefnic monomer or complex olefnic mixtures(including C4/C5/C9 fractions)in large quantities,which open a new way to transform huge amount of unused olefnic compounds in C4/C5/C9 fractions into valuable copolymers,and(2)the resultant polymeric NPs possess a self-limiting size and narrow size distribution,therefore being one of the most simple,efcient,and green strategies to produce uniform,size-tunable,and functional polymeric nanoparticles.More importantly,the separation of the NPs from the reaction medium is simple and the supernatant liquid can be reused;hence this new synthetic strategy has great potential for industrial production.
Zhenjie LiuDong ChenJinfang ZhangHaodong LiaoYanzhao ChenYingfa SunJianyuan DengWantai Yang
