杂多酸引发四氢呋喃聚合反应Ⅴ.生长链浓度与链生长速率常数的测定

采用改进的酚钠法及端羟基测定法对环氧乙烷促进的低浓度磷钨杂多酸引发的四氢呋喃聚合反应过程中生长链浓度的测定表明 ,杂多酸分子中的三个质子均参与了引发反应 ,各引发一个聚合链 .采用醋酸酐为促进剂时杂多酸引发四氢呋喃聚合反应生长链浓度测定的结果也证明了这一点 .由此测得在 0℃和 2 0℃时四氢呋喃聚合反应链增长表观速率常数分别为 3 78× 10 -3 和 1 98× 10 -2 L·mol-1·s-1,这与四氢呋喃按离子型生长链增长时的反应速率常数相近 .说明PW12 引发的THF聚合反应是通过氧离子活性中心增长的     

聚四氢呋喃三元醇的合成及表征

合成了一种新的三元引发剂[C₂H₅C(CH₂OCH₂CH₂CO+ClO₄^-)₃],并用于制备聚四氢呋喃三元醇.用¹HNMR,FTIR和GPC法对聚合物的结构进行了表征.结果表明,产物中环状齐聚物的含量极低.对聚合物水解产物的分子量及分子量分布测定结果表明,产物为预期的三元醇,聚合反应过程中链转移可以忽略,聚合物的分子量可控.     

Indian Turmeric and its Use in Cationic Photopolymerizations

Curcumin, an intensely yellow dye isolated from Indian turmeric is an excellent electron-transfer photosensitizer for cationic vinyl and ring-opening polymerizations. Especially attractive features of curcumin are its strong absorption, broad spectral sensitivity, efficient electron-transfer, low toxicity and low cost. Using curcumin as a photosensitizer, the cationic photopolymerizations of a variety of monomers were carried out including such naturally derived monomers as epoxidized terpenes and epoxidized vegetable oils. The impact of this technology on applications such as housing, boat-building and water distribution is discussed.     

Cationic Ring-Opening Polymerization of 1,3-Dehydroadamantanes

Ring-opening polymerizations of [3.3.1]propellane derivatives, 1,3-dehydroadamantane ( 1 ) and 5-butyl-1,3-dehydroadamantane ( 2 ), were carried out with CF₃SO₃H in CH₂Cl₂ at 0 °C for 6–42 h. The central σ-bonds in 1 and 2 were exclusively opened to afford novel poly([3.3.1]propellane)s, poly(1,3-adamantane)s, in 52–95% yields. The resulting poly( 2 ) possessing flexible butyl substituent was soluble in chloroform, THF, and 1,2-dichlorobenzene, and the degree of polymerization was estimated to be greater than 30, while the poly( 1 ) was hardly soluble in the common organic solvents. All aliphatic poly( 1 ) and poly( 2 ) showed high thermal stability, their 10% weight loss temperatures were 421 and 486 °C, respectively.     

Conditions to Control Furan Ring Opening during Furfuryl Alcohol Polymerization

The chemistry of biomass-derived furans is particularly sensitive to ring openings. These side reactions occur during furfuryl alcohol polymerization. In this work, the furan ring-opening was controlled by changing polymerization conditions, such as varying the type of acidic initiator or the water content. The degree of open structures (DOS) was determined by quantifying the formed carbonyl species by means of quantitative ¹⁹F NMR and potentiometric titration. The progress of polymerization and ring opening were monitored by DSC and FT-IR spectroscopy. The presence of additional water is more determining on ring opening than the nature of the acidic initiator. Qualitative structural assessment by means of ¹³C NMR and FT-IR shows that, depending on the employed conditions, poly(furfuryl alcohol) samples can be classified in two groups. Indeed, either more ester or more ketone side groups are formed as a result of side ring opening reactions. The absence of additional water during FA polymerization preferentially leads to opened structures in the PFA bearing more ester moieties.     

Phosphazene/Lewis Acids as Highly Efficient Cooperative Catalyst for Synthesis of High-Molecular-Weight Polyesters by Ring-Opening Alternating Copolymerization of Epoxide and Anhydride

The synthesis of high-molecular-weight polyesters via the ring-opening alternating copolymerization (ROAC) of cyclic anhydrides and epoxides using organocatalysts remains a major challenge. In this context, the organic cyclic trimeric phosphazene base ( CTPB ) was used as an efficient catalyst for the ROAC of phthalic anhydride (PA) with epoxides. It was found that the activity and PA conversion dramatically increased with the addition of triethyl borane (TEB) as a cocatalyst, even a small amount of TEB, for example, 5 mol % relative to CTPB . The molecular structures of obtained polyesters were characterized by nuclear magnetic resonance (¹H NMR, ¹³C NMR) and matrix-assisted laser desorption/ionization time-of-flight (MALDI TOF), which demonstrated the formation of perfectly alternating polyesters with unimodal and narrow molecular weight distributions. Different molecular weight polyesters (up to 118.5 kg mol⁻¹) were facilely prepared by reducing the loading of CTPB and TEB, while the polymerizations were fast (turnover frequency, TOF up to 500 h⁻¹). Thermal analysis of the resulting polymers indicated that the alternating polyesters were amorphous, and their T_gs increased with the increment of molecular weights. © 2020 Wiley Periodicals, Inc. J. Polym. Sci. 2020 , 58, 803–810     

In-chain functionalized poly(ε-caprolactone): A valuable precursor towards the synthesis of 3-miktoarm star containing hyperbranched polyethylene

Well-defined 3-miktoarm star copolymer 3μ-HBPE(PCL)₂ (HBPE: hyperbranched polyethylene, PCL: poly[ε-caprolactone]) was synthesized by combining chain walking polymerization (CWP), ring-opening polymerization (ROP), and “click” chemistry. The synthetic methodology includes the following steps: (a) synthesis of in-chain ethynyl-functionalized PCL, (PCL)₂-C ≡ CH by ROP of ε-caprolactone (CL) with ethylene-functionalized solketal (3-[prop-2-yn-1-yloxy] propane-1,2-diol) as difunctional initiator and phosphazene superbase t-BuP₂ as catalyst; (b) synthesis of azido-functionalized hyperbranched PE (HBPE-N₃) by CWP of ethylene with α-diimine-Pd(II) catalyst, followed by quenching with excess 4-vinylbenzyl chloride and transformation of chloro to azide group with sodium azide; and (c) “clicking” HBPE-N₃ and (PCL)₂-C ≡ CH using copper(I)-catalyzed azide–alkyne cycloaddition. ¹H NMR spectroscopy, gel permeation chromatography, Fourier-transform infrared spectroscopy, and differential scanning calorimetry were used to determine the molecular characteristics and thermal properties of the polymers. Self-assembly behavior of 3μ-HBPE (PCL)₂ in petroleum ether, a selective solvent for HBPE, was investigated by dynamic light scattering, atomic force microscopy, and transmission electron microscopy. The in-chain alkyne-functionalized poly(ε-caprolactone) is a valuable precursor for PCL-based complex macromolecular architectures.     

两亲性聚氨基酸三嵌段共聚物构筑pH/溶剂可控多级纳米结构

通过开环聚合（ROP）和原子转移自由基聚合（ATRP）合成了一种pH响应性三嵌段共聚物聚乙二醇-b-聚赖氨酸-b-聚苯乙烯（PEG-b-PLL-b-PS），在水-有机溶剂混合溶液中进行组装，并采用透射电子显微镜（TEM）、原子力显微镜（AFM）和衰减全反射红外光谱法（ATR-IR）表征.该三嵌段共聚物在四氢呋喃（THF）与水的混合溶剂（V：V=1：1）中可组装成疏水性聚苯乙烯为核、亲水性聚赖氨酸和聚乙二醇分别为内壳和外壳的球状胶束.采用TEM和AFM发现该球状胶束在四氢呋喃（THF）水溶液中退火7 d后可进一步转变为纤维状结构.进一步除去THF后，可恢复至粒径略小的冻结球状胶束.另外，球状胶束的粒径随着pH的增加而增加，当pH为13时，聚赖氨酸的二级结构由无规卷曲构象过渡到α-螺旋构象，聚集体由球形结构过渡到空心囊泡.溶液经透析后可使囊泡恢复至球状胶束.     

DFT study of the role of substituents in tin(II) bis(amidoethyl)amine complexes used for ε-caprolactone polymerization

DFT simulations of ring-opening polymerization of ε-caprolactone in the presence of two stannylenes based on bis(2-amidoethyl)amine ligands demonstrated that rate limiting step of the whole process is the nucleophilic attack of a metal initiator with the formation of the tetrahedral carbon from sp² carbon atom of the carboxy group. The presence of electron-withdrawing groups at the terminal nitrogen atoms of the ligands leads to decrease in the activation energy of the rate limiting step.