COLLOID AND POLYMER SCIENCE
·
2012
·Vol. 291
·期 4
·789-803
·
IF 2.331
Zhang Xiaojing,Wang Chaojun,Fang Shaoming,Sun Jiashu,Li Chong,Hu Yuelei
In this paper, a series of hybrid star PLLA (sPLLA) with different arm lengths was synthesized via the hydrosilylation between octakis(dimethylsiloxy) silsesquioxane (Q 8 M 8 ) and functionalized PLLA macromolecules with vinyl end groups (mPLLA). mPLLA was synthesized by ring-opening polymerization of l -lactide using 2-hydroxyethylmethacryl as an initiator in the presence of stannous 2-ethylhexanoate as a catalyst. The obtained sPLLA has low polydispersity with polydispersity index values from 1.29 to 1.30. The arm numbers of sPLLA vary from 5 to 7 and decrease with the increase in the length of the mPLLA arm due to the steric hindrance, which are estimated by 1 H NMR analysis. The branched structure of sPLLA is also evidenced by the lower intrinsic viscosity when compared with the linear mPLLA with similar molecular weight. Both the glass transition temperatures ( T
g ’s) and melting temperatures ( T
m ’s) of sPLLAs are higher than those of the mPLLA arms. The incorporation of polyhedral oligomeric silsesquioxane (POSS) does not change the crystalline structure of PLLA, while the crystallinity of sPLLA is enhanced as the result that the POSS core acts as a heterogeneous nucleating agent in the matrix to promote the crystallization ability of PLLA. High-resolution transmission electron microscopy observation suggests that POSS disperses in the crystalline PLLA matrix as 5–20 nm aggregates. Microspheres of sPLLA with mean diameter 1 to 2 μm were prepared via emulsion solvent evaporation method. The sPLLA microspheres have higher loading capacity and encapsulation efficiency and lower drug release rate than mPLLA microspheres.
研究领域:
材料科学
·
药物递送
·
高分子化学
✓ 已验证
产品关联
DOI
高影响因子
FOOD HYDROCOLLOIDS
·
2021
·
IF 9.147
Rui Wang,Mei Li,Jinguang Liu,Fenfen Wang,Jing Wang,Zhongkai Zhou
The effect of dual modifications of pullulanase debranch and propionylation on rice starch property was investigated in this study. The occurrence of the propionylation in starch molecules was confirmed due to the formation of a new peak at 1750 cm −1 in FTIR spectrum and the characteristic peaks around 1.0 (methyl) and 2.2 (methylene) ppm in NMR compared with the native starch. Interestingly, because of the higher tendency of molecular retrogradation following the debranching, the current results revealed that there was no positive correlation between the amylose content (AC) and the debranching time. Debranching treatment increased the degree of substitute (DS) of the propionyl starch, and the AC was positively correlated with DS (R = 0.7753*), indicating that AC is an important element affecting propionyl reaction due to the exposure of more available hydroxyl groups during debranching. Meanwhile, debranching led to an increased crystallinity level and the crystallinity pattern changed from A-type to B-type, which is associated with the changes in their corresponding hydrolysis resistance. The NMR data also proved that the propionylation involves the replacements of the glucose in the starch structure (C-2, C-3 and C-6) with acyl groups of the desired complexes. Furthermore, the sequence of the reactions that occur in the process of propionylation and their mechanisms are proposed in the current study.
研究领域:
食品科学
·
生物化学
✓ 已验证
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DOI
高影响因子
Sustainable Energy & Fuels
·
2018
·Vol. 2
·期 8
·1855-1862
·
IF 0
Jiajin Liang,Jiao Chen,Shubin Wu,Chao Liu,Ming Lei
Comprehensive understanding of cellulose pyrolysis is critical to valuable chemical and liquid fuel generation in biomass-based biorefining processes. Herein, a specific tubular reactor was designed to observe the cellulose appearance alteration corresponding to the chemical structure evolution in various pyrolysis stages. The appearance of cellulose changed from white powder to light brown powder below 300 °C as its crystal lattice thermal expansion and the degree of crystallinity decrease. Cellulose began to depolymerize at 300 °C accompanied with the dehydration of pinacol and primary product levoglucosan generation. 325–350 °C was the critical pyrolysis stage for cellulose. The intermediate state was formed accompanied with a series of thermochemical reactions. All the typical signals from FTIR, 13C CP/MAS NMR disappeared when the temperature was up to 350 °C. The percentages of C, H, and O conversion to the volatile products were up to 35%, 55% and 60%, respectively, along with β-1,4-glycosidic bond cleavage, decarboxylation, and decarbonylation reactions. Meanwhile, CO2, CO, and CH4 were measured using a thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer (TG-FTIR) in the slow pyrolysis process. The increasing C/H and C/O ratios in the carbonation stage enhanced the aromaticity of biochar. Furthermore, electron paramagnetic resonance (EPR) analysis indicated that it tended to form carbon-centered radicals.
研究领域:
生物质能
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化学工程
·
材料科学
✓ 已验证
产品关联
DOI
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
·
2023
·
IF 8.2
Yumiao Ma,Yikelamu Jilili,Tengfei Shao,Weijun Zhen
Poly(lactic acid) (PLA) has its own limitations in terms of slow crystallization rate and low crystallinity during processing, resulting in poor toughness and thermal stability , which seriously restricts the practical application of PLA. Blending nanoparticles into the PLA matrix is an effective way to improve PLA crystallization. In this study, carbon dots (CDs) were prepared by green oxidation using weathered coal as carbon source and then surface-modified with dodecylamine (DDA) and octadecylamine (ODA). Modified CDs (MCDs)/PLA composite films were prepared using MCDs as filler to improve the crystallinity and toughness of PLA films. The results showed that the improvement effect of ODA-modified CDs (ODACDs) was better than that of DDA-modified CDs (DDACDs). The crystallinity of PLA composite film (0.05 wt% ODACDs) was increased from 7.20% (pure PLA film) to 35.44%, and its elongation at break was increased by 5.01 times compared with that of the pure PLA film. Moreover, thermogravimetric analysis suggested that the thermal stability of MCDs/PLA films was also improved. The results of simultaneous rheology and in-situ FTIR analysis as well as molecular dynamics simulations confirmed that MCDs had a strong interaction with PLA molecules, which promoted the crystallization of PLA film, thereby improving its toughness and thermal stability.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Polymers
·
2024
·Vol. 16
·期 5
·630
·
IF 4.7
Xiang Li,Qiao Xu
In this work, the EVOH/Ti3C2composite fibers were prepared via electrospinning and the effect of added Ti3C2on the structure and properties of electrospun EVOH fibrous membranes was further investigated. The morphology, crystal structure, thermal properties, wettability, tensile properties, as well as air permeability and water vapor permeability of as-prepared EVOH/Ti3C2composite fibers were studied. The Ti3C2is uniformly loaded onto the surface and inside the composite fiber and affects the fiber diameters. Furthermore, The Ti3C2self-orients along the fiber axis and does not change the crystal structure of the electrospun EVOH fibers, improving the crystallinity and thermal stability of the electrospun EVOH/Ti3C2fibrous membranes. With the increase in the Ti3C2concentration in the electrospinning polymer solution, the addition of Ti3C2not only rapidly improves the wettability of the fibrous membranes, but also enhances their air permeability, compared with the pristine electrospun EVOH fibrous membranes. The experimental results provide theoretical guidance for the preparation of Ti3C2composite fibers, and also expand the application of electrospun EVOH and EVOH/Ti3C2fibrous membranes.
研究领域:
材料科学
·
纳米技术
✓ 已验证
DOI
PubMed
高影响因子
STARCH-STARKE
·
2021
·
IF 2.741
Xiaofei Shi,Yueping Ding,Jie Wan,Chengmei Liu,Sangeeta Prakash,Xue Xia
Annealing is a hydrothermal treatment that changes the structural and functional properties of starches. This study investigates and compares the effects of one-step annealing for 24 and 48 h, respectively, and two-step annealing on the structural, physicochemical, and digestive properties of Castanopsis sclerophylla starch (CaS). Annealing has no effect on CaS morphology, crystalline pattern, and short-range ordered structures. However, annealing decreases the swelling power, solubility, setback, and peak viscosity of CaS and increases its crystallinity and thermal stability. Post annealing, the rapidly digestible starch (RDS) of CaS decreases, the slowly digestible starch (SDS) increases while the resistant starch (RS) content of CaS remains unchanged. Comparing with One-step annealing for 24 h, one-step annealing for 48 h and two-step annealing does not further change the RDS and SDS content of annealed CaS.
研究领域:
食品科学
·
植物学
✓ 已验证
产品关联
DOI
高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
·
2019
·Vol. 136
·期 33
·47887
·
IF 2.188
Tiantang Fan,Wuyou Ye,Beibei Du,Qin Zhang,Li Gong,Jiafeng Li,Shengli Lin,Zhongyong Fan,Qing Liu
A series of high-molecular-weight terpolymers named PTG- b -LG and PT- b -LG were synthesized based on the macroinitiators of PTG copolymers and PTMC, respectively. In vitro degradation of PTG- b -LG and PT- b -LG was carried out by immersing into PBS, in comparison with that of P L LA. Mass loss, water uptake, GPC, DSC, WAXD, and 1 H NMR were examined for the degradation study. It was found that PTG- b -LG degraded faster than PT- b -LG and P L LA due to the Di -random block structure, which had lower regularity of chain and lower crystallinity. The compositional changes appeared to be more complex, but the molar mass decreased owing to chain fragmentation caused by hydrolysis. Moreover, morphological changes were also observed during the degradation in all situations with the crystallization of by-products and a preferential degradation of amorphous domains. Specifically, PTG- b -LG presented an adjustable degradation rate and may be used for the fabrication of totally biodegradation stents in the future. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136 , 47887.
研究领域:
材料科学
·
生物医学工程
✓ 已验证
产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF BIOLOGICAL MACROMOLECULES
·
2017
·
IF 3.671
Binghua Sun,Yaoqi Tian,Benxi Wei,Long Chen,Yanhong Bi,Zhengyu Jin
Potato starch was treated with 0.36% HCl in ethanol and water for various time periods, and its structural changes were evaluated and compared in this study. Acid-ethanol treated starch (AET-s) had relatively low average molecular weight ( M w ) and z-average radius of gyration ( R g ), and its solubility was higher than that of the counterpart acid-water treated starch (AWT-s). The granular appearance and differential scanning calorimetry (DSC) profile demonstrated that acid in ethanol and in water exhibited different attack pathways on the granules. No significant difference in crystallinity was observed for AET-s; however, the ratio of absorbance 1022/995 cm −1 and the peak intensity detected by small-angle X-ray scattering (SAXS) were increased with increasing treatment time. These results suggested that ethanol-acid treatment simultaneously attacked on the amorphous and crystalline regions, and the degradation extent on crystalline regions caused by ethanol-acid treatment was higher than that observed by acid-water treatment.
研究领域:
食品科学
·
生物化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
FOOD HYDROCOLLOIDS
·
2014
·
IF 4.28
Xiuting Hu,Hongyan Li,Benxi Wei,Xueming Xu,Zhengyu Jin,Yaoqi Tian
The aim of this study was to examine 1-buatnol–hydrochloric acid (1-butanol–HCl) hydrolysis process of starch . Normal rice starch was hydrolyzed by 0.36% HCl in anhydrous 1-butanol at 40 °C from 4 h to 7 days. The changes in starch granule, crystalline, and molecular weight during the 1-butanol–HCl hydrolysis were determined using SEM, particle size analyzer, XRD, HPSEC–MALLS–RI, and iodine staining. SEM and particle size analyzer analysis showed that the granule morphology significantly changed and the granule size decreased from 5.47 μm to 5.07 μm after the hydrolysis by 1-butanol–HCl for 7 days. XRD results indicated that amorphous areas of normal rice starch were firstly hydrolyzed followed by the ordered areas during 1-butanol–HCl hydrolysis. The peak (2 θ ) of V-type crystallinity was detected at around 20° in the XRD curves of 1-butanol–HCl-hydrolyzed starches. This peak confirmed the formation of amylose–1-butanol complex. HPSEC–MALLS–RI and iodine staining analysis demonstrated that the weight-average molecular weight of normal rice starch sharply decreased from 2.4 × 10 7 Da to 4.9 × 10 5 Da after 1-butanol–HCl hydrolysis for 4 h, then gradually decreased, and finally stabilized at about 2.6 × 10 4 Da after hydrolysis for 4 days. These results suggest that the attack of 1-butanol–HCl on normal rice starch preferentially occurred in the amylopectin molecules of amorphous areas.
研究领域:
食品科学
·
生物化学
✓ 已验证
产品关联
DOI
高影响因子
BIORESOURCE TECHNOLOGY
·
2014
·
IF 5.039
Yanjuan Zhang,Qian Li,Jianmei Su,Ye Lin,Zuqiang Huang,Yinghua Lu,Guosong Sun,Mei Yang,Aimin Huang,Huayu Hu,Yuanqin Zhu
A new technology for the pretreatment of natural cellulose was developed, which combined mechanical activation (MA) and metal salt treatments in a stirring ball mill. Different valent metal nitrates were used to investigate the changes in degree of polymerization (DP) and crystallinity index (CrI) of cellulose after MA + metal salt (MAMS) pretreatment, and Al(NO 3 ) 3 showed better pretreatment effect than NaNO 3 and Zn(NO 3 ) 2 . The destruction of morphological structure of cellulose was mainly resulted from intense ball milling, and the comparative studies on the changes of DP and crystal structure of MA and MA + Al(NO 3 ) 3 pretreated cellulose samples showed a synergistic interaction of MA and Al(NO 3 ) 3 treatments with more effective changes of structural characteristics of MA + Al(NO 3 ) 3 pretreated cellulose and substantial increase of reducing sugar yield in enzymatic hydrolysis of cellulose. In addition, the results indicated that the presence of Al(NO 3 ) 3 had significant enhancement for the enzymatic hydrolysis of cellulose.
研究领域:
生物化学
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF POLYMER RESEARCH
·
2015
·Vol. 22
·期 11
·1-8
·
IF 1.92
Chen Feng,Kan Ze,Hua Sun,Liu Zhengying,Yang Mingbo
A study has been made on an attempt to further expand the current knowledge in melt processing of cellulose. The basic idea is that a few zinc compounds may remain in the regenerated cellulose by formation of a zinc-cellulose complex and hydrolysis reaction when ZnCl 2 molten hydrates are used as a solvent for cellulose. The chance is that zinc compounds may act as isolation agents to destroy the hydrogen bonding and reduce the crystallinity of cellulose. Interesting results revealed that the raw cellulose and regenerated celluloses in our work showed different structures and other, but specific, thermal behavior, admitting that the melting of cellulose was not detected. The results are preliminary but demonstrate that simply destroying the hydrogen bonding and reducing the crystallinity will promote the dehydration of cellulose at a lower temperature, since the activity of the cellulose hydroxyls would be improved unexpectedly in that condition. It is expected that this study will stimulate some new ideas to make some progress in the melt processing of this material.
研究领域:
材料科学
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
INTERNATIONAL JOURNAL OF POLYMER ANALYSIS AND CHARACTERIZATION
·
2023
·
IF 1.9
Ting Hu,Yujun Wang,Jingwei Lin,Zhanyong Wang
Poly(butylene succinate) (PBS), poly(hexamethylene succinate) (PHS) and three kinds of poly(butylene succinate-co-hexamethylene succinate)s (P(BS-co-HS)s) were enzymatically hydrolyzed by Fusarium solani cutinase. The results showed that the characteristics of the enzymatic hydrolysis of these polyesters were mainly affected by crystallinity, thermal properties and the BS/HS ratio. The enzymatic hydrolysis rates of the polyesters are as follows: P(BS-co-HS52) ≈ P(BS-co-HS71) > PHS > P(BS-co-HS32) > PBS. Furthermore, with increasing HS content, both the degree of crystallinity (Xc) and melting temperature (Tm) of the polyesters first decreased and then increased. P(BS-co-HS52) and P(BS-co-HS71) had the lowest Xc and the lowest Tm, thus had the highest hydrolysis rate; this shows that the hydrolysis rate is affected by Xc and Tm. The results also showed that BS/HS ratio could affect the physical properties and degradability of polyesters. Thus, it is possible to prepare polyesters with various physical properties and degradability for different applications by adjusting BS/HS ratio. The crystalline and amorphous regions of the polyesters were both hydrolyzed, during which parts of the crystalline regions were converted into the amorphous regions. Finally, we found that the crystal structure and thermal stability of the polyesters were not affected by the enzymatic hydrolysis.
研究领域:
生物化学
·
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）