Soft Matter
·
2016
·Vol. 12
·期 8
·2473-2480
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IF 3.798
Lei Hou,Qijing Chen,Zesheng An,Peiyi Wu
The lower critical solution temperature (LCST) transition in water and the upper critical solution temperature (UCST) transition in ethanol of poly(oligo(ethylene glycol) acrylate) (POEGA)-based core cross-linked star (CCS) polymers have been investigated and compared by employing turbidity, dynamic light scattering (DLS), 1H NMR and FTIR measurements. Macroscopic phase transitions in water and in ethanol were observed to occur when passing through the transition temperature, as revealed by DLS and turbidity measurements. Analysis by IR indicated that the interactions between the polymer chains and solvent molecules in water are stronger than those in ethanol such that the CCS polymer arm chains in water adopt more extended conformations. Moreover, hydrophobic interaction among the aliphatic groups plays a predominant role in the LCST-type transition in water whereas weak solvation of the polymer chains results in the UCST-type transition in ethanol. Additionally, the LCST-type transition in water was observed to be much more abrupt and complete than the UCST-type transition in ethanol, as suggested by 1H NMR and IR at the molecular level. Finally, an abnormal “forced hydration” phenomenon was observed during the LCST transition upon heating. This study provides a detailed understanding of the subtle distinctions between the thermal transitions of CCS polymers in two commonly used solvents, which may be useful to guide future materials design for a wide range of applications.
研究领域:
高分子化学
·
材料科学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF MOLECULAR LIQUIDS
·
2024
·
IF 5.3
Hongyu Guo,Linfang Liang,Jiayi Guo,Liangbin Lin,Fafu Yang
The metal-coordination self-assemble system played an important role on constructing novel supramolecular smart-response materials. Although the single and double-response materials based on metal-induced self-assembly had been studied extensively, the triple responses for this kind of supramolecular material was seldom reported. In this work, the first metal-induced self-assemble system with triple responses on photophysical, liquid crystalline and gel properties was presented based on Hg 2+ -coordination tetraphenylene dimer ( Bis-TPE ). Bis-TPE was prepared by bridging two alkyl-substituted tetraphenylene with amido chain. It possessed the fluorescence response from the strong emission for Bis-TPE to the faint emission for Bis-TPE -Hg 2+ complex. The self-assemble mechanism of Bis-TPE -Hg 2+ was clarified as that Hg 2+ was located in the cavity of the amido-ether chain of Bis-TPE . The Hg 2+ -induced mesomorphic transition was also observed from smectic mesophase for Bis-TPE to hexagonal columnar mesophase for Bis-TPE -Hg 2+ complex. The unique Hg 2+ -induced gel transition was further distinguished from low-order spherical morphology for Bis-TPE to high-order fibrous morphology for Bis-TPE -Hg 2+ complex. The maximum fluorescence wavelength exhibited the giant shift from 494 nm for Bis-TPE in gel to 606 nm for Bis-TPE -Hg 2+ in gel. This kind of triple responses on photophysical, liquid crystalline and gel properties for metal-coordination self-assemble system was described for the first time, affording a new idea on design of new multiple-response materials with unique properties.
研究领域:
超分子化学
·
材料科学
·
配位化学
✓ 已验证
DOI
高影响因子
Aggregate
·
2023
·Vol. 4
·期 5
·e363
·
IF 18.8
Xiaoqing Liu,Zhihui Shi,Feng Yu,Chao Teng,Chen Zhang,Zhong-Ren Chen
The precipitate and the coacervate are two aggregated states in the polyelectrolyte complexes (PECs). The precipitate-to-coacervate transition and glass transition in PECs have been widely reported in the past. In many cases, the two phenomena are studied independently, although both of them are apparently affected by water and small ions. Here, utilizing a PEC system consisting of poly(acrylic acid) (PAA) and a cationic bolaamphiphile (DBON), we explore the states of PECs as a function of salt, temperature, and the molecular weight of PAAs. By a combination of microscopic observation, time-resolved fluorescence measurements, and differential scanning calorimetry, we identify salt/temperature driven precipitate-to-coacervate transitions of the complexes. The thermally induced morphology transformation from the precipitate to coacervate occurs around the glass transition temperature, indicating a strong correlation between the two processes. As the molecular weight of the PAA increases, the thermal transition temperature becomes higher. This finding offers new insights on the mechanistic interactions that dictate the aggregated states of PECs. Based on the photothermal effect of DBON, we also develop a UV light-induced strategy to mediate the precipitate-to-coacervate transition, providing a fantastic platform to create functional PEC materials.
研究领域:
材料科学
·
生物物理学
✓ 已验证
产品关联
DOI
高影响因子
Journal of the American Chemical Society
·
2022
·
IF 16.383
Shasha Liu,Mengqi Lv,Haoran Li,Sa Wang,Chengdong Feng,Xiaoliang Wang,Wenbing Hu,Wei Wang
An ultrathin surface layer with extraordinary molecular mobility has been discovered and intensively investigated on thin-film polymer materials for decades. However, because of the lack of suitable characterization techniques, it remains largely unexplored whether such a surface mobile layer also exists on individual polymeric nanospheres. Here, we propose a thermal-optical imaging technique to determine the glass transition (Tg) and rubber-fluid transition (Tf) temperatures of single isolated polystyrene nanospheres (PSNS) in a high-throughput and nonintrusive manner for the first time. Two distinct steps, corresponding to the glass transition and rubber-fluid transition, respectively, were clearly observed in the optical trace of single PSNS during temperature ramping. Because the transition temperature and size of the same individuals were both determined, single nanoparticle measurements revealed the reduced apparent Tf and increased Tg of single PSNS on the gold substrate with a decreasing radius from 130 to 70 nm. Further experiments revealed that the substrate effect played an important role in the increased Tg. More importantly, a gradual decrease in the optical signal was detected prior to the glass transition, which was consistent with a surface layer with enhanced molecular mobility. Quantitative analysis further revealed the thickness of this layer to be ∼8 nm. This work not only uncovered the existence and thickness of a surface mobile layer in single isolated nanospheres but also demonstrated a general bottom-up strategy to investigate the structure–property relationship of polymeric nanomaterials by correlating the thermal property (Tg and Tf) and structural features (size) at single nanoparticle level.
研究领域:
材料科学
·
光学成像
·
纳米技术
✓ 已验证
DOI
PubMed
高影响因子
JOURNAL OF SOLID STATE CHEMISTRY
·
2023
·
IF 3.3
Jia Luo,Yuqing Luo,Jun Tan,Hongsheng Che,Ting He,Jiugang Hu
The large-scale and controllable production of boehmite has attached much attention due to its extensive application in advanced energy and electronics industries. In this study, a facile vaporthermal (VPH) method was developed for the rapid fabrication of rhombic boehmite microflakes using low-cost commercial gibbsite particles. The evolution behaviors of gibbsite to boehmite under VPH and conventional hydrothermal (LPH) conditions were ex-situ monitored by XRD , Raman, and FT-IR techniques. The boehmite powders from VPH (V-boehmite) and LPH (L-boehmite) have similar crystal structure and bonding vibration information, whereas V-boehmite exhibits rhombic morphology and L-boehmite presents cubic morphology. Moreover, the formation time of boehmite can be shortened from 16 h of LPH to 6 h of VPH at 180 °C, which significantly contributes to its scalable production. These differences of V-boehmite are attributed to the direct contact between high-temperature saturated water steam and gibbsite, which can induce the rapid formation of rhombic boehmite microflakes through dissolution-recrystallization mechanism. Therefore, the vaporthermal technology has great potential for efficient, sustainable, and large-scale production of boehmite powders.
研究领域:
材料科学
·
能源技术
✓ 已验证
产品关联
DOI
高影响因子
Journal of Physical Chemistry C
·
2019
·
IF 4.309
Caiju Chen,Mengling Liao,Beibei Shan,Ming Li
A fundamental understanding of the thermal stability of vacancy-doped cuprous telluride nanocrystals (Cu2–xTe NCs) will be conductive to their exploitation in plasmon-related applications. However, the thermally induced structural and Raman spectral changes of Cu2–xTe NCs have remained fairly unexplored so far. Here, temperature-induced structural transitions of Cu2–xTe nanowires (NWs) are studied by in situ Raman spectroscopy from −190 to 530 °C. Results reveal a dramatic temperature dependence of Raman signatures of Cu2–xTe NWs, serving as a potent indicator for their structures and structural transitions. The hexagonal weissite-to-orthorhombic phase transition takes place in the cooling process from 25 °C to −190 °C. An intermediate state of high degree of disorder with featureless Raman spectra is observed before its dissociation into the elemental Cu and the high-temperature phase above 480 °C. This work provides fundamental insights into the thermally induced structural stability of Cu2–xTe NWs and will further stimulate new exploration of their plasmon-related practical applications.
研究领域:
材料科学
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纳米技术
·
光谱学
✓ 已验证
产品关联
DOI
高影响因子
CRYSTENGCOMM
·
2019
·Vol. 21
·期 38
·5749-5756
·
IF 3.382
Wen Zeng,Haojie Lai,Tianyin Chen,Yueheng Lu,Zhihong Liang,Tingting Shi,Ke Chen,Pengyi Liu,Fangyan Xie,Jian Chen,Jianbin Xu,Qiulan Chen,Weiguang Xie
VO2 particles with a reduced size enable the optimization of its metal–insulator transition (MIT) temperature and hysteresis width. The accurate modulation of particle size and the underlying mechanism of transition behavior remains a critical issue. In this study, the annealing process of a V2O5 precursor film was systematically controlled with the guidance of the V–O phase diagram. The film undergoes a synergistic solid-state dewetting and pyrolysis process in the first step to form dispersed VO2 particles, and then a crystallization process to achieve the preferred orientation, which allows fine control of the particle size and crystallinity by thickness control of the precursor film. Then, the MIT behavior of VO2 particles with controlled sizes from 220 nm to 1.64 μm was systematically investigated. With decreasing size, the MIT temperature decreases and then increases with enlarged hysteresis. A minimum MIT temperature of 41 °C without hysteresis was realized. Size dependent crystallinity, strain and defect analyses showed that compressive stress dominates the MIT behavior of larger sized particles, while surface tensile stress and surface defect effects become prominent in smaller sized particles. This work provides a feasible strategy to control the size effect of dispersed VO2 particle films and deepen our understanding on the MIT behavior in single domains.
研究领域:
材料科学
·
凝聚态物理
·
纳米科技
✓ 已验证
DOI
高影响因子
JOURNAL OF POLYMER SCIENCE PART B-POLYMER PHYSICS
·
2017
·Vol. 55
·期 18
·1373-1379
·
IF 2.838
Jiao Chen,Ye Sha,Siyang Gao,Chao Teng,Xiaoliang Wang,Dongshan Zhou,Linling Li,Wei Chen,Gi Xue
Understanding the conformational changes of polymeric chains in solutions is an essential and integral part of polymer physics. By increasing the concentration of polymer solutions from dilute to semidilute regime, the critical chain overlapping has been reported at the concentration termed as C *. In this study, the associated inter- and intrachain conformational transitions in polystyrene (PS) solutions are reported. By comparing the spectroscopic intensity ratio versus concentration for an intrachain PS system, a break point was observed in good solvent which coincided with the theoretically predicted C *. Moreover, the intrachain conformation showed no obvious change below C *, while significant collapse started to occur above C *. This result reveals a new insight in polymer physics, since traditionally the size of polymer chains is considered to decrease weakly regarding the concentration change in the semidilute regime. It is important to find such an abrupt intrachain conformational transition between the dilute and semidilute solutions and provide the first experimental observation that inter- and intrachain conformational transitions are correlated to one the other. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55 , 1373–1379
研究领域:
聚合物物理
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
DYES AND PIGMENTS
·
2017
·
IF 3.473
Yunjian Wang,Wanying Wu,Xianliang Fu,Mingzhu Liu,Jing Cao,Congying Shao,Shifu Chen
This work explores the phase transition and its impact on photoluminescent properties of metastable scheelite-type, with and without Eu 3+ doped, CdWO 4 nanophosphors. A series of scheelite structure CdWO 4 :xEu 3+ (x = 0, 0.025, 0.05, 0.075, 0.10) samples were synthesized using a simple solvothermal method. The X-ray diffraction results indicate that the prepared samples were single phase in a tetragonal scheelite-type structure, and completely transformed into pure monoclinic wolframite structure after sintering at 450 °C for 2 h. It was revealed by Rietveld analysis that Eu 3+ doping induced a lattice contraction of both scheelite and wolframite CdWO 4 structures. The impact of Eu 3+ doping on the crystal structure and the band structure were further probed by FT-IR, Raman and UV–Vis spectroscopy. SEM images show that the morphology of the prepared samples also changed in the phase transition and the Eu 3+ doping processes. All samples showed a broad multi-color luminescence emission in the range from 400 to 640 nm under 280 nm excitation. The relative intensities of the blue-green emission originated from CdWO 4 matrix and the red emission ascribed to Eu 3+ can be regulated by both the crystal structure and Eu 3+ doping levels. The energy transfer process between WO 4 groups in scheelite structure CdWO 4 and WO 6 groups in wolframite structure CdWO 4 and Eu 3+ was discussed in detail based on the photoluminescent excitation and emission spectra. The synthetic approach reported here allows the control over CdWO 4 polymorphs and this kind of luminescent material has wide applications in white-LED, chemosensors and bioimaging .
研究领域:
材料科学
·
光学
✓ 已验证
产品关联
DOI
高影响因子
Materials Today Communications
·
2023
·
IF 3.8
Jianhui Su,Yan Liu,Xiujing Peng,Guoxin Sun,Xuchuan Jiang
Due to the high activation energy barrier and the sporadic nature of nucleation, the temperature required for the transition from cubic dense γ-Al 2 O 3 to tripartite α-Al 2 O 3 is as high as 1100–1200 °C. In this work, a two-step strategy was employed to reduce the phase transformation temperature, and prepare α-Al 2 O 3 particles with good dispersion. As the first step, 10 nm sheet γ-Al 2 O 3 was obtained by ammonium aluminum carbonate (AACH) decomposition, which was more favorable to the crystal transformation in the next ball-milling processing. In the second step, γ-Al 2 O 3 powder with partial α-Al 2 O 3 produced in situ by ball-milling γ-Al 2 O 3 was calcined, and α-Al 2 O 3 nanoparticles were obtained at just 850 °C. The content of the α-Al 2 O 3 is determined by the Rietveld Refine method. The relationship between ball-milling time and α-Al 2 O 3 content was clarified, and the effect of α-Al 2 O 3 content on the transformation temperature and morphology of γ-Al 2 O 3 was discussed. The results showed that the α-Al 2 O 3 content rises with the increase of ball milling time, and spherical α-Al 2 O 3 nanoparticles can be obtained when the α-Al 2 O 3 content is 5 %. The addition of α-Al 2 O 3 seeds reduces the phase transition temperature but agglomeration exists. Our proposed two-step low-temperature calcination strategy is an important method for the preparation of alumina nanoparticles
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 BIOLOGICAL MACROMOLECULES
·
2024
·
IF 7.7
Kairong Wu,Hao Zhang,Xinjiang Lou,Xiaodan Wu,Ying Wang,Kuangyu Zhao,Xin Du,Xiufang Xia
The structure, physicochemical and anti-freeze properties of natural deep eutectic solvent (NADES) composed of inulin and L-proline (molar ratio of 1:11) were investigated. Proton nuclear magnetic resonance ( 1 H NMR), Fourier infrared spectroscopy (FTIR), and Raman spectroscopy revealed extensive hydrogen bonding in the pure NADES system, and the addition of water weakens the hydrogen bonding interactions between the components. The smaller transverse relaxation time ( T 2 ) represents the stronger hydrogen bond strength, and NADES+40 % H 2 O exhibited a large T 2 (71.68 ms). When 10 % water was added, the viscosity decreased from 3620 mPa·s to 1777 mPa·s, but the conductivity increased to approximately twice the original value. Furthermore, adding 10 % water lowered the glass transition temperature (T g ) of NADES by 5.6 °C. NADES+10 % H 2 O exhibited favorable thermal stability and freezing resistance, as evidenced by the fact that approximately 82.61 % of the ice crystals area <200 μm 2 after 30 min of crystallization . The changes in the structure, physicochemical, and anti-freezing properties of water-tailored NADES are expected to enable the design of novel antifreeze agents.
研究领域:
食品科学
·
物理化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Materials Today Chemistry
·
2025
·
IF 6.7
Zicheng Yuan,Xiaoqin Zhang,Fei Liu,Xianliang Jiang,Hao Wang,Jin Zhu,Jinggang Wang
High glass transition temperature polymers are extensively used in many fields such as packaging, electronic products, and automobiles. However, most of them are expensive as synthesized in polar aprotic solvent with low solid percent. The task of effectively synthesizing high glass transition temperature polymers faces at least three important challenges: the need for a solvent-free process to reduce cost and pollution, the requirement for a thermoplastic process with a high glass transition temperature above 150 °C, and the use of monomers derived from renewable resources. Traditional polyesters can be prepared via melt polycondensation, but achieving a glass transition temperature above 130 °C while maintaining good mechanical properties remains challenging. In this work, we developed a strategy to synthesize a new high glass transition temperature polyesters by employing rigid bulky diol of 9,9-bis [6-(2-hydroxyethoxy)naphthyl]fluorene (BNEF) and bio-based 2,5-furandicarboxylic acid (FDCA) which derived from fructose or furfural, as the main monomers. The new copolyesters exhibit a glass transition temperature of up to 164.2 °C, a number-average molecular weight of 24,600 g/mol, along with tensile modulus and strength values of 3030 MPa and 134 MPa, respectively. Furthermore, the copolyesters exhibit excellent transparency properties of 88.4 % by cutoff at 700 nm and well solvent resistance, which could serve as new low-cost, high-performance engineering plastics with ultra-high glass transition temperature and transparency.
研究领域:
材料科学
·
聚合物化学
✓ 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）