MACROMOLECULAR CHEMISTRY AND PHYSICS
·
2024
·
IF 2.5
Yiyin Yang,Lei Zhang,Fansen Meng,Donglin Tang
ZnO is considered to be a good catalyst for the synthesis of polyurethanes (PUs) by alcoholysis of bisureas (BUs). ZnO tends to form Zn(NCO) 2 (NH 3 ) 2 in the presence of urea at high temperature, so does it in the alcoholysis of BUs. Here, attempt is made to understand the role Zn(NCO) 2 (NH 3 ) 2 plays in the alcoholysis of BUs. A loading of Zn(NCO) 2 (NH 3 ) 2 at 5 mol% is found to be sufficient to catalyze the polymerization and the reaction time is greatly cut from 40 h (catalyzed by ZnO) to 26 h, with similar chemical structures and properties. The tensile strength, elongation at break, and toughness for PU–Zn-5 can reach 43.8 MPa, 330%, and 94.0 J cm −3 , respectively. One-pot synthetic strategy is then further introduced to improve the efficiency of the polymerization. Zn(NCO) 2 (NH 3 ) 2 , BU, and PU can be synthesized in one-pot, by adding ZnO, urea, diamine, LiBr, and diol sequentially. The feasibility of this one-pot method is verified, indicated by the similar reaction time, chemical structures, molecular weight, thermal and mechanical properties. This one-pot synthetic strategy offers an efficient way to synthesize PUs directly and simply from urea, diamines, and diols, which is beneficial for improving the molecular diversity of PUs.
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
CHINESE JOURNAL OF POLYMER SCIENCE
·
2018
·Vol. 36
·期 10
·1150-1156
·
IF 2.016
Qiu Wei-Guang,Zhang Fei-Long,Jiang Xu-Bao,Kong Xiang-Zheng
Polyureas (PU) are well known as a class of high impact engineering materials, and widely used also in emerging advanced applications. As a general observation, most of them are only soluble in a very limited number of highly protonic solvents, which makes their chemical structure analysis a great challenge. Besides the presence of abundant hydrogen bonding, the poor solubility of PU in common organic solvents is often ascribed to the formation of biuret crosslinking in their molecular chains. To clarify the presence of biuret groups in PU has been of great interest. To this end, two samples, based on hexamethylene diisocyanate (HDI) and toluene diisocyanate (TDI) respectively, were synthesized by precipitation polymerization of each of these diisocyanates in water-acetone at 30 °C. Their chemical structures were analyzed by high resolution magic angle spinning (HR-MAS) NMR, and through comparison of their NMR spectra with those of specially prepared biuret-containing polyurea oligomers, it was concluded that biuret group was absent in all the PU prepared at 30 °C. In addition, this NMR analysis was also applied to a PU obtained by copolymerization of TDI with ethylene diamine (EDA) and water at 65 °C in EDA aqueous solution. It was confirmed that biuret unit was also absent in this PU and that EDA was more active than water towards TDI. The presence of EDA was crucial to the formation of uniform PU microspheres. This study provides therefore a reliable method for the analysis of PU chemical structure.
研究领域:
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
·
2017
·
IF 2.843
Xubao Jiang,Xiaoli Zhu,Alexandre A. Arnold,Xiang Zheng Kong,Jerome P. Claverie
Owing to the presence of abundant interchain interactions such as hydrogen bonds, polyureas (PU) are only swellable or soluble in a limited number of highly protonic solvents, and the viscosity of the solutions obtained is very high, making their chemical structure characterization hard or even impossible by standard NMR. Accurate structure analysis is also hard by solid-state NMR due to low spectral resolution. The presence of a side reaction in their synthesis generating biuret cross-links is often invoked to explain their insolubility. Here we demonstrate that High Resolution Magic Angle Spinning (HR-MAS) NMR is an efficient tool for the chemical structure analysis even for cross-linked PU. With 1H, 13C, and 1H–15N HSQC combined, a variety of linear and cross-linked PU is analyzed by HR-MAS NMR, and conclusive information on their chemical structure is obtained, which reveals for the first time that the biuret group is absent in all PU.
研究领域:
材料科学
·
分析化学
✓ 已验证
产品关联
DOI
高影响因子
MACROMOLECULAR CHEMISTRY AND PHYSICS
·
2023
·Vol. 224
·期 8
·2200448
·
IF 2.5
Yiyin Yang,Kangzhou Xie,Donglin Tang
Alcoholysis of bisureas (BUs) would be of great potential among the non-isocyanate routes for preparing polyurethanes, if the issue of the high melting temperature and the poor solubility for BUs can be solved. In this study, it is proposed to introduce Li salt to assist the melting of BUs via a eutectic system. It is found that the melting point of BUs indeed can be reduced to 170 °C or even lower by adding 40 mol% of LiCl or LiBr. In the polymerizations of BUs with diols, it is found that ZnO nanoparticles (30 ± 10 nm) are the most efficient catalyst in the catalyst screening study. Four polyurethanes are successfully synthesized and the glass transition temperature of them is detected to be 34–45 °C. PU1010 is tougher than other polymers so that it is able to be molded. The Young's modulus of PU1010 is 195.1 MPa, while the strength and the elongation at break are 36.4 MPa and 280%, respectively. The toughness calculated is 67.3 J cm −3 . This Li salt-assisted melting strategy not only realizes the synthesis of polyurethanes through alcoholysis of BUs, but can also be extended to the synthesis of other high performance polymers.
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
Soft Matter
·
2017
·Vol. 13
·期 45
·8609-8617
·
IF 3.889
Suansuan Wang,Kaiqiang Liu,Sheng Gao,Jinqiang Wang,Ravi Kumar Marella,Yu Fang
A new class of bisurea derivatives bearing tetrahydroxy groups have been proven to be non-gelators in water and various organic solvents even under long-term sonication or efficient heating treatment. We found that it is possible to trigger physical gelation behaviour by constructing dynamic covalent bonding. The results show that formation of dynamic covalent bonding between the borate anion and ethanediol substituent in these bisurea derivatives brings about rapid physical gelation at ambient temperature in a mixture of DMSO and water. During dynamic covalent bonding-triggered gelation, the stepgrowth polymerization from the B–O bonds would increase the size of the molecules and reduce the entropy of mixing as well as facilitate ion–dipole interactions in the linear polymeric gelators. They would drive a self-assembly transition and boost the construction of gel networks in coordination with α-tape urea–urea hydrogen bonding. The gelation mechanism was explored by 1H NMR, FTIR and rheology techniques. Moreover, the resulting gels are transparent and thixotropic, and could be turned into the sol state under CO2 or water-stimulus. Furthermore, they are stable in the presence of HAuCl4 and alkali. Therefore, they would afford another new medium for the growth of Au nanocrystals via in situ reduction and a new sensing medium for detecting Hg2+ ions.
研究领域:
化学
·
材料科学
·
纳米技术
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
·
2018
·Vol. 57
·期 2
·90-100
·
IF 2.588
Fanfan Du,Ying Zheng,Wenhua Yuan,Guorong Shan,Yongzhong Bao,Suyun Jie,Pengju Pan
Development of effective organocatalysts for the living ring-opening polymerization (ROP) of lactones is highly desired for the preparation of biocompatible and biodegradable polyesters with controlled microstructures and physical properties. Herein, a new class of hydrogen-bond donating bisurea catalysts is reported for the ROP of lactones under solvent-free conditions. ROP of lactones mediated by the bisurea/7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD) catalyst exhibits a living/controlled manner, affording the polymers and copolymers with the well-defined structure, predictable molecular weight, narrow molecular weight distribution, and high selectivity for monomer at low catalyst loadings at ambient temperature. The possible mechanism of bisurea/MTBD-catalyzed ROP of lactones is proposed, in which the bisurea activates the carbonyl group of lactones while MTBD facilitates the nucleophilic attack of the initiating/propagating alcohol by hydrogen bonding. Moreover, the poly(ε-caprolactone- co -δ-valerolactone) [P(CL- co -VL)] random copolymers with various compositions were synthesized using the bisurea/MTBD catalyst. The measurements of thermal properties and crystalline structure demonstrate that the CL and VL units are cocrystallized in the crystalline phase of P(CL- co -VL) copolymers. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57 , 90–100
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
MACROMOLECULAR CHEMISTRY AND PHYSICS
·
2022
·Vol. 223
·期 7
·2100452
·
IF 2.996
Kangzhou Xie,Donglin Tang,Guangzhao Zhang
Nonisocyanate polyurethanes (NIPUs) are nowadays considered as green alternatives to conventional polyurethanes, without using the toxic isocyanates. NIPUs usually are synthesized from cyclic carbonates and di(poly)amines. Herein a novel pathway toward polyurethane vitrimers (PUVs) based on epoxide (1,4-butanediol diglycidyl ether, BDE) and alkylene bisureas (BUs) is reported, which can easily be prepared from renewable urea and diamines. Due to the high melting temperature and the poor solubility, BUs are rarely applied in the synthesis of polyurethanes. To enhance the mellability of BUs, ZnCl 2 is introduced to form eutectic system and therefore to assist melting of BUs (eutectic-assisted melting). When 100 mol% of ZnCl 2 is added, BUs are able to melt at 130 °C at which polymerization between BUs and BDE is then triggered and can be finished within 10 min. Interestingly, the obtained polymers are found to be polyurethane vitrimers, for which the relationship between the relaxation time ( τ *) and the temperature ( T ) fits with Arrhenius equation. PUV-10 samples before and after reprocessing remains similar appearance and mechanical properties ( E : ≈90 MPa; σ b : ≈17 MPa; ε b : ≈200%). A new synthetic strategy is apparently offered here for NIPUs and even for PUVs without adding any crosslinker.
研究领域:
材料科学
·
绿色化学
✓ 已验证
产品关联
DOI
高影响因子
ADVANCED FUNCTIONAL MATERIALS
·
2024
·
IF 18.5
Junwen Deng,Deyu Liu,Haiqi Liu,Linxuan Yu,Yunhao Bai,Jinsheng Xiao,Huiliang Wang
The development of persistent room-temperature phosphorescent (pRTP) hydrogels is important for the practical applications of organic phosphors. Unfortunately, the phosphorescence emission of nontraditional luminogens (NTLs) can be strongly quenched by water in hydrogel networks. Herein, a series of pRTP organohydrogels based on NTLs are prepared by dissolving poly(vinyl alcohol) (PVA), biuret (BIU) and poly(maleic acid) (PMAc) (or other nonaromatic macromolecular acids) in a glycerol/water mixed solvent, followed by a simple freezing-thawing treatment. Very impressively, the organohydrogel exhibits remarkable excitation-dependent and metal cation-responsive phosphorescence with a maximum lifetime up to 782.8 ms at ambient conditions. Moreover, the organohydrogels treated with metal cations also have excitation-dependent phosphorescence. Multidimensional information encryption can be achieved by simply printing solutions of metal cations onto the gel surface and switching the irradiation lights, or using gel blocks prepared with different macromolecular acids. Structural characterizations, mechanical tests, and comparative studies prove that hydrogen bonding between BIU and macromolecular chains leads to rigidification of molecular conformations and the cooperative effect of the components leads to the pRTP of the organohydrogels. This work provides a reliable strategy for the preparation of nonaromatic phosphorescent hydrogels with long afterglows and greatly expands the practical applications of phosphorescent materials.
研究领域:
材料科学
·
化学
·
光学
·
纳米技术
✓ 已验证
产品关联
DOI
高影响因子
PARTICLE & PARTICLE SYSTEMS CHARACTERIZATION
·
2023
·Vol. 40
·期 10
·2300049
·
IF 2.7
Dong Yan,Zhiying Zhang,Yun Liu,Yan Guan,Dongming Sun
Since 2015, m-phenylenediamines (mPD) have become a popular carbon source for the synthesis of carbonized polymer dots (CPDs). However, their exact fluorescence mechanism is still obscure. To elucidate this, inorganic acids that are carbon-free are chosen as additives for a comparative study. It is found that the green fluorescence quantum yield (nearly 80%), photostability, and reaction yield (over 90%) can be enhanced by introduction of most of inorganic acids with moderate amount. Besides, green-blue dual emission is observed in acid-assisted groups. UV-vis absorption, Fourier-transform infrared spectroscopy, and surface-enhanced Raman scattering results indicate that the green fluorescence center is composed of quinoid rings, whereas the blue fluorophore contains benzenoid rings. Moreover, room-temperature afterglow with lifetime up to 1.25 s is observed exclusively in acid-assisted CPDs composites with urea/biuret. The blue chromophore is proposed to be the origin of the triplet level that induces the long afterglow. This work provides an in-depth understanding on the macromolecular structures of CPDs derived from phenylenediamines, and contributes a new line of thought to the origin of phosphorescence in N-doped carbon dots.
研究领域:
材料科学
·
化学
·
光学
✓ 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）