MACROMOLECULES
·
2021
·
IF 5.985
Hanqing Jiang,Shengda Wang,Yanhui Wang,Yaxian Wang,Liang Li,Li Ma,Dongmei Cui,Tao Tang
A new strategy to access long-subchain hyperbranched polypropylene (LHB-PP) has been established, starting from the thermally degraded polypropylene (PP) possessing two-terminal vinylidene double bonds of isopropenyl end groups (PP-TVD). PP-TVD reacts with hydrogen bromide (HBr) with high efficiency, followed by a substitution reaction with sodium azide to yield azide-terminated PP (PP-N3). Finally, the highly efficient click reaction between PP-N3 and 1,3,5-triethynylbenzene (TEB) affords the unprecedented LHB-PP, of which the molecular weight and topologic microstructure are well controlled by tuning the (PP-N3)-to-TEB molar ratios. Compared to the linear PP with a similar molecular weight, the solution of this newly obtained LHB-PP has a lower intrinsic viscosity and a smaller hydrodynamic radius. Simultaneously, the LHB-PP melt presents a higher zero shear viscosity and a more apparent shear-thinning phenomenon. For solid properties, there are γ crystalline components in the LHB-PP, and the lamellar thickness of LHB-PP is much smaller than that of linear PP. This work paves a new avenue for upgrading the recycled PP to new products with hyperbranched topology and improved properties.
研究领域:
材料科学
·
高分子化学
✓ 已验证
DOI
高影响因子
JOURNAL OF MEMBRANE SCIENCE
·
2019
·
IF 7.015
Jiafei Liu,Xiaoming Yan,Li Gao,Lei Hu,Xuemei Wu,Yan Dai,Xuehua Ruan,Gaohong He
To achieve a better performance of anion exchange membranes (AEMs), AEMs of a unique structure with flexible and dense side chains are prepared by taking amino groups on poly (aryl ether ketone)s (PAEKs) as reaction sites and grafting four long side chains on each repeat unit of main chains. This chemical synthetic route for the unique structure is simple and controllable, with no obvious side reactions happening during synthetic process. Three different kinds of cycloaminium cations are used as functional groups. The AEMs with this unique structure exhibit limited swelling ratios and improved hydroxide conductivities, of which the highest attains 74.4 mS cm −1 at 80 °C when using N-Methylmorpholine (Mm) as the cation group. The high conductivities are due to the formation of connective ion conducting channels facilitated by this kind of structure inside the membranes. No obvious changes in chemical structures of AEMs with different cations happen after alkali treatment for 768 h at 60 °C, indicating a good alkaline stability of AEMs with such specific structure. Moreover, the PAEK-MmOH yields a maximum power density of 302 mW cm −2 at 640 mA cm −2 when operating in a single fuel cell. Overall, these long-branched and densely functionalized AEMs with cycloaminium cation groups possess good application prospects in fuel cells.
研究领域:
材料科学
·
化学工程
·
能源科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
·
2013
·Vol. 51
·期 10
·2142-2149
·
IF 3.543
Chen He,Ban-Kun Jin,Wei-Dong He,Xue-Song Ge,Jing Tao,Jing Yang,Sheng-Qi Chen
Long-subchain hyperbranched polystyrene (lsc-hp PSt) with uniform subchain length was obtained through copper-catalyzed azide-alkyne cycloaddition click chemistry from seesaw macromonomer of PSt having one alkynyl group anchored at the chain centre and two azido group attached to both chain ends [alkynyl-(PSt-N 3 ) 2 ]. After precipitation fraction, different portions of lsc-hp PSt having narrow overall molecular weight distribution were obtained for further grafting with alkynyl-capped poly( N -isopropylacrylamide) (alkynyl-PNIPAM), which was obtained via single-electron transfer living radical polymerization of NIPAM with propargyl 2-bromoisobutyrate as the initiator and grafted onto the peripheral azido groups of lsc-hp PSt via click chemistry. Thus, amphiphilic lsc-hp PSt grafted with PNIPAM chains (lsc-hp PSt- g -PNIPAM) was obtained and would have star-like conformation in tetrahydrofuran (THF). By replacing THF with water, lsc-hp PSt- g -PNIPAM was dissolved at molecular level in aqueous solution due to the hydrophilicity of PNIPAM and exhibited thermal induced shrinkage of PNIPAM arms. The water-insoluble lsc-hp PSt would collapse densely and could be served as a reservoir to absorb hydrophobic chemicals in aqueous solution. The influence of overall molecular weight of lsc-hp PSt on the absorption of pyrene was studied. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013
研究领域:
高分子化学
·
材料科学
✓ 已验证
DOI
高影响因子
MACROMOLECULES
·
2019
·
IF 5.997
Nairong Hao,Xiaozheng Duan,Hongjun Yang,Ahmad Umair,Mo Zhu,Muhammad Zaheer,Jinxian Yang,Lianwei Li
This work aims to elucidate how the branching effect of macromonomer influences the polymerization, structural features, and solution properties of ABn long-subchain hyperbranched polymers (LHPs). Our result reveals that compared with linear AB2 macromonomers, star AB3 macromonomers result in the suppression of chain extension, and the enhancement of macromonomer self-cyclization during the preparation of LHPs by “click” polymerization, due to the branching-enhanced steric hindrance effect. The combined triple-detection SEC and stand-alone LLS studies of unfractionated and fractionated AB3 LHPs unambiguously demonstrate their statistically fractal nature. Namely, the intrinsic viscosity ([η]) and radius of gyration (Rg) are scaled to the macromonomer molar mass (Mmacro) and the total molar mass (Mhyper) as [η] = Kη,AB3MhyperνMmacroμ (ν ≃ 0.39, μ ≃ 0, and Kη,AB3 ≃ 0.29 mL/g) and Rg = HR,AB3MhyperαMmacroβ (α ≃ 0.47, β ≃ 0, and HR,AB3 ≃ 3.6 × 10–2 nm). Surprisingly, [η] and Rg are both almost independent of Mmacro (μ ≃ 0 ≃ β), indicating a similar draining property and local segment density for LHPs with different subchain lengths, which is different from the classic AB2 systems (μ ≃ 0.3 and β ≃ 0.1). A comparison of results for ABn LHPs (n = 2, 3) and short-subchain hyperbranched systems indicates that the fractal dimensions (f) for LHPs are generally smaller than short-subchain systems, whereas f is not sensitive to the local segment density or branching pattern. A combination of experimental observation and Langevin dynamics simulation of ABn dendrimers and LHPs further reveals (i) the segment back-folding phenomenon is prominent only for ABn (n ≥ 3) LHPs systems because it is mainly dominated by the macromonomer branching effect, rather than the internal subchain length, and (ii) the trend for segment interpenetration increases remarkably as Mmacro increases for both dendrimers and LHPs. The result also indicates that the unique synergistic effect of segment back-folding and segment interpenetration in AB3 system is the most probable reason for the observed Mmacro independent solution properties. Specifically, because of the unique synergistic effect, small macromonomer/oligomer chains can interpenetrate more easily into hyperbranched oligomer chains composed of longer subchains and subsequently “click” couple with the back-folded segments in the interior space of LHPs, which eventually could lead to a similar draining property and local segment density for AB3 LHPs with different subchain lengths.
研究领域:
高分子化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
·
2016
·Vol. 54
·期 21
·3462-3469
·
IF 3.114
Sheng-Qi Chen,Lulu Xu,Chen He,Peng-Yun Li,Xiao-Xia Lu,Jia-Min Li,Hui-Juan Li,Wei-Dong He,Lihua Yang
The emergency of antibiotic-resistant bacteria and their wide spread has posed a worldwide threat to public health, and traditional antibiotics are gradually overwhelmed by infectious bacteria. Herein, we report an efficient and economical strategy to construct antimicrobial polymers with net cationic component and hyperbranched architecture, which exhibit highly selective toxicity toward bacteria over human cells. To this aim, cationic poly(aminoethyl acrylate) (PAEA) without hydrophobicity is chosen for low hemolysis activity and targeting the negative bacterial membranes, and hyperbranched architecture is introduced to solve the dilemma of low antimicrobial activity. Long-subchain hyperbranched PAEA ( lhb -PAEA) samples kills >99.99% gram-negative Escherichia coli and >98% gram-positive Staphylococcu aureus at the dose of ≤4 μg/mL. Moreover, lhb -PAEA samples exhibit great biocompatibility, for the hemolysis percentage was ≤35% even at the high dose of 1024 μg/mL. Thus, enhanced antimicrobial activity, reduced hemolytic toxicity, the feasible and low-cost production are achieved for lhb -PAEA as antimicrobial agents. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54 , 3462–3469
研究领域:
生物材料学
·
微生物学
·
医学
✓ 已验证
DOI
高影响因子
Polymer Chemistry
·
2018
·Vol. 9
·期 20
·2830-2842
·
IF 4.927
Mo Zhu,Nairong Hao,Jinxian Yang,Lianwei Li
V-type (B∼∼A∼∼B) and Y-type (A∼∼∼∼B2) macromonomer approaches are two of the most widely adopted synthetic methodologies for the preparation of long-subchain hyperbranched polymers (LHPs) with a controlled subchain length. However, little attention has been paid to the difference of the structural regularity of hyperbranched polymers prepared via the two approaches in previous related studies. This work aims to elucidate how these two synthetic approaches quantitatively influence the polymerization, branching pattern and solution properties of the prepared hyperbranched polymers. First, two sets of model hyperbranched polystyrenes (HPSV and HPSY) were prepared from V-type and Y-type macromonomers by a combination of atom transfer radical polymerization (ATRP) and azide–alkyne cycloaddition coupling reaction, respectively. The intrachain cyclization study indicated that the macromonomer self-cyclization during the interchain coupling process was strongly affected by the chain length and the structure of the used macromonomer as well as the reaction concentration. The V-type macromonomer was found to be less inclined to undergo interchain coupling due to the stronger steric hindrance effect. Furthermore, via triple-detection size exclusion chromatography (TD-SEC) characterization, the intrinsic viscosity ([η]) and the radius of gyration (Rg) were found to be scaled to the molar mass of the macromonomer (Mm) and the molar mass of the entire chain (Mt) as [η] = KηMtνMmμ (μ ≃ 0.25 and ν ≃ 0.40) and Rg = HRMtαMmβ (α ≃ 0.47 and β ≃ 0.083) for both HPSV and HPSY samples. These scaling relationships evidenced that both HPSV and HPSY hyperbranched structures hold a similar statistically fractal feature. More importantly, the determined values of ratios Kη,Y/Kη,V (∼1.5) and HR,Y/HR,V (∼1.2) demonstrated, for the first time, that the average equivalent length of the branching subchain (Ls) for HPSY is much longer than the initial macromonomer chain length (Lm), i.e. Ls = 2.5Lm while Ls is exactly equal to 1/2Lm for HPSV. This finding clearly clarified the difference between Ls and Lm, and thus the terms of Ls and Lm should not be misused in the future structure–property study. Finally, the value of the Rg/Rη ratio is determined to be ∼1.05 and ∼1.15 for HPSV and HPSY samples (Rη: viscometric radius), respectively, which are much smaller than the typical values for linear chains in good solvents (1.20–1.40), revealing the less draining nature of these hyperbranched structures.
研究领域:
高分子化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）