Wenhuan Wang,Lin Sang,Qingbo Guan,Yiping Zhao,Zhiyong Wei,Yang Li
Biodegradable polyesters with X-ray visibility for biomedical applications have attracted increasing attention. We herein reported a facile method of end-chain functionalization to prepare highly branched linear-comb poly (lactic acid) (Lc-PLA) using triiodobenzoic acid (TIBA) as end-capping and X-ray contrast agent. Three branch lengths of iodinated linear-comb poly (lactic acid) (I-Lc-PLA 30k , I-Lc-PLA 50k , and I-Lc-PLA 70k ) were successfully synthesized and then microspheres with well-controlled size (average size ~180 μm) were prepared. By micro-CT testing, the results showed that shorter branch length of PLA contributed more iodinated end-group functionalized sites, leading a relatively high iodine content and excellent radiopacity. After terminated with TIBA, glass transition temperature and thermal stability of I-Lc-PLA polymers were greatly improved. During the in vitro hydrolytic degradation of three months, the molecular weight , iodine content, surface microstructure and micro-CT radiopacity of these microspheres were investigated. The degradation results showed that I-Lc-PLA 50k possessed sufficient iodine content and high household unit values, suggesting a well-maintained radiopacity of I-Lc-PLA. Therefore, this work proposed a highly branched I-Lc-PLA microspheres with promising CT-imaging capacity, which could be used as a long-term embolic material.
Jiangpeng Ni,Meishao Hu,Dong Liu,Huixiong Xie,Xiongzhi Xiang,Lei Wang
Highly branched polymers applied as low-temperature proton exchange membranes (LTPEMs) have attracted attention from researchers because of their outstanding properties. However, there are few reports on the use of branched polymers as high-temperature proton exchange membranes (HTPEMs). In this work, a series of highly branched polybenzimidazoles (PBIs) with 1,3,5-tri(4-carboxyphenoxy)benzene (B3) as a branching agent were designed and successfully synthesized for the first time. The highly branched PBIs were soluble in polar organic solvents and could be cast to form tough and smooth films. Compared with linear PBI membranes, the branched PBI membranes with a 9% degree of branching exhibited a high phosphoric acid (PA) doping level of 10.5 (PA molecules per repeat unit), high proton conductivity (0.043 S cm−1) at 180 °C under anhydrous conditions, high resistance to oxidation and good PA retention ability. All these properties indicate that branched PBI membranes are promising for HTPEMs and can be potentially used in HTPEM fuel cells.
Ting Hu,Qilin Huang,Kahing Wong,Hong Yang,Jingsi Gan,Yanru Li
An alkali-soluble polysaccharide was extracted from Lignosus rhinocerotis sclerotia (LRP). Its structural characteristics were determined by GC–MS, FT-IR, GC, 1D and 2D NMR combined with Smith degradation and methylation analysis. The LRP had a (1 → 3)-β- d -Glcp backbone with every three residues bearing a (1 → 6)-linked and hyperbranched side chain that contained three (1 → 6)-β- d -Glcp residues as secondary main chain and two terminal β- d -Glcp residues linked at O3. The degree of branching was 0.76 from GC–MS analysis, implying a highly branched structure for LRP. The M w , < S 2 > z 1/2 , R h and [ η ] values of LRP in 0.25 M LiCl/DMSO were measured by SEC-MALLS-Vis-RI combination technology to be 2.88 × 10 5 g/mol, 30.36 nm, 22.34 nm and 131.50 ml/g, respectively. Furthermore, the exponent α of [ η ] –M w , β of < S 2 > z 1/2 –M w , the fractal dimension d f and molecular parameter ρ were determined to be 0.20, 0.33, 2.50 and 1.36, demonstrating that the LRP was a hyperbranched polysaccharide and adopted a compact coil conformation in LiCl/DMSO.
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