官能团化聚己内酯的合成与表征

通过分子结构设计合成了新型含有侧基官能团的聚己内酯材料.首先,通过亲核加成反应,由溴乙酸乙酯与烯胺合成2-乙氧甲酰甲基环己酮;然后以间氯过氧化苯甲酸为氧化剂,通过Baeyer-Villiger氧化反应,得到带有官能团的己内酯单体,6-乙氧甲酰甲基-ε-己内酯;该单体在异辛酸亚锡(Sn(Oct)2)的催化下,本体开环聚合得到相应的均聚物及其与ε-己内酯的共聚物.采用1H-NMR、13C-NMR、GPC和DSC表征了聚合物的结构和热力学性能.随着6-乙氧甲酰甲基-ε-己内酯在共聚物中的含量增加,共聚物的分子量降低,同时熔点和熔融焓也随之降低.     

Characterization of microbial poly (ε-l-lysine) by FT-IR, Raman and solid state C NMR spectroscopies

The molecular structure and conformation of microbial poly(ε-l-lysine) (M-ε-PL) produced by a variant of Streptomyces albulus were studied by means of FT-IR, FT-Raman and solid-state ¹³C NMR spectroscopies. Vibrational results indicate that M-ε-PL assumes a β-sheet conformation in the solid state. Solid state ¹³C NMR spectra of the crystalline and the amorphous components were observed separately and the degree of crystallinity was estimated to be 63%. A plausible conformation model was proposed.     

聚ε-己内酯结晶形态的研究

采用DSC测试了聚ε-己内酯(PCL)的结晶温度(TC)和熔融温度(Tm)。同时采用偏光显微镜(POM)探讨了结晶时间的影响,发现结晶时间的改变只能够改变其晶体的尺寸,对其结晶形态并没有太大的影响。最后采用原子力显微镜(AFM)讨论了基底材料、溶剂和过冷度对PCL结晶形态的影响。结果表明:基底材料对PCL结晶形态的影响是比较显著的,PCL在硅片上呈棒状,在云母和涂有碳膜的云母上呈树枝状。溶剂对PCL结晶形态的影响明显,其结晶形态的差别与蒸汽压有关。在不同的温度下PCL结晶形态都成树枝状晶体,且分枝宽度随着过冷度的降低而增加。     

羟基酸引发ε-己内酯开环聚合的研究

研究了水、醇、羧酸存在下ε 己内酯开环聚合的情况 ,发现在适当温度下 (80℃ ) ,羧基并不引发ε 己内酯的开环聚合 ,但对羟基引发ε 己内酯开环聚合起加速作用 ,而且催化能力与酸度有关 .进而又对羟基酸(乙醇酸、DL 苹果酸、柠檬酸 )引发ε 己内酯开环聚合做了研究 ,合成了一系列含不同数目遥爪羧基的α 羟基 ω 羧基 (1,2 ,3)己内酯低聚物 (HCPCL) ,并对其结构做了酸值滴定、羟值滴定、UV、FTIR与1H NMR分析 .对羧基催化羟基引发ε 己内酯开环聚合的机理做了分析     

New ε-caprolactone diyne monomers aiming for biodegradable polymers

A substitution reaction of cyclohexane-1,4-diol with propargyl bromide gave 4-(prop-2-yn-1-yloxy)cyclohexanol. This compound was oxidized to the corresponding ketone (2-C₂H) and then to acetylene γ-substituted ε-caprolactone (3-C₂H). The latter compound was chain-extended to two butadiynyl monomers: symmetrical 5,5′-[hexa-2,4-diyne-1,6-diylbis(oxy)]bis(oxepan-2-one) (3-C₄-3) and unsymmetrical 5-{[5-(trimethylsilyl)penta-2,4-diyn-1-yl]oxy}oxepan-2-one (3-C₄TMS) via Eglinton and Cadiot–Chodkiewicz couplings, respectively. Both compounds were obtained through an alternative Baeyer–Villiger oxidation of immediate ketone precursors 2-C₄-2 and 2-C₄TMS.     

Preparation and Characterization of Poly(L-lactide-co-glycolide-co-ε-caprolactone) Scaffolds by Thermally Induced Phase Separation

Abstract

The technique of thermally induced phase separation (TIPS) is favorable for the fabrication of a porous scaffold due to a number of advantages. In this work the poly(L-lactide-co-glycolide-co-ε-caprolactone) (PLLGC) terpolymer was synthesized by melt copolymerization and porous scaffolds thereof from its solution in 1,4-dioxane were fabricated by using the TIPS method. The effects of fabrication parameters, including polymer concentration and freezing temperature, on the morphology, pore size and mechanical properties were studied. The results showed that the average pore size of the PLLGC porous scaffold increased with a decrease in PLLGC concentration and the pore size resulting from freezing at 4?°C (about 20–100?μm) was significantly larger than for other samples (20–50?μm) frozen at lower temperatures. The porosity of the scaffolds decreased with increasing PLLGC concentration or decreasing freezing temperature. On the other hand, the compressive strength of the scaffolds increased with the increase of PLLGC concentration or the decrease of freezing temperature, as would be expected. The present results can be applied in design to control the processing parameters of TIPS for a scaffold with desired pore morphology.     

A facile synthesis of hydrophilic poly(ε-caprolactone)-based poly(ether-ester-amide)s

Segmented poly(ether-ester-amide)s, (PEEA)s, of controlled hydrophilicity degree, based on poly(ε-caprolactone) (PCL), were synthesized according to a facile two-step procedure using α,ω-dihydroxy oligomeric PCL, 4,7,10-trioxa-1,13-tridecanediamine and macromers prepared from poly(ethylene glycol)s and adipoyl chloride. The PEEAs showed M _n values in the range 5–11.5 kDa. A PCL-type crystallinity was found by WAXS. DSC indicated T_m values (49–51 °C) close to that of PCL macromer. Single glass transitions were observed both by DSC and DMTA techniques and the T_g values (−58–−50 °C by DSC) were slightly higher than that of PCL. The water uptake was in the range 4.8–26.0 wt.-% depending on the length of the poly(ethylene glycol) segment.

Monomers used to prepare the PEEAs.     

Electrowetting — From statics to dynamics

More than one century ago, Lippmann found that capillary forces can be effectively controlled by external electrostatic forces. As a simple example, by applying a voltage between a conducting liquid droplet and the surface it is sitting on we are able to adjust the wetting angle of the drop. Since Lippmann's findings, electrocapillary phenomena – or electrowetting – have developed into a series of tools for manipulating microdroplets on solid surfaces, or small amounts of liquids in capillaries for microfluidic applications. In this article, we briefly review some recent progress of fundamental understanding of electrowetting and address some still unsolved issues. Specifically, we focus on static and dynamic electrowetting. In static electrowetting, we discuss some basic phenomena found in DC and AC electrowetting, and some theories about the origin of contact angle saturation. In dynamic electrowetting, we introduce some studies about this rather recent area. At last, we address some other capillary phenomena governed by electrostatics and we give an outlook that might stimulate further investigations on electrowetting.     

Poly(ε-caprolactone)-based hyperbranched polyurethanes prepared via A2 + B3 approach and its shape-memory behavior

Novel hyperbranched shape-memory polyurethanes based on ε-caprolactone were prepared via A₂ + B₃ approach with different molecular weights (M_w); the molecular weights ranged from 7.2 × 10⁴ to 32.3 × 10⁴ g/mol. The hard segment content was varied minimally and the B₃ monomer was also varied. The polymers were characterized by GPC, DSC, DMA, WAXD and shape-memory test. The crystallinity calculated from DSC and WAXD data indicated that the highly branched architecture does not affect the crystallization of these polymers. More interestingly the storage modulus ratios (E′ ratios) of hyperbranched polymers were found to be significantly high compared to the linear analogue. As a consequence, hyperbranched polymers show 100% more shape-recovery rate compared to their linear counterpart. Antimicrobial susceptibility tests confirmed that these polymers have good antimicrobial activity which is an essential requirement of medical implants.     

Synthesis and molecular structure of new heterometal alkoxide clusters Ln2Na8(OCH2CF3)14(THF)6 (Ln = Sm, Y, Yb): Highly active catalysts for polymerization of ε-caprolactone and trimethylene carbonate

The new polynuclear heterometal alkoxide clusters Ln₂Na₈(OCH₂CF₃)₁₄(THF)₆ (Ln = Sm 1, Y 2, Yb 3) have been synthesized by the reaction of anhydrous LnCl₃ with 7 equiv. of NaOCH₂CF₃ in 68–75% yields. Crystal structural analysis revealed clusters 1–3 are isomorphous composed of two cubanes and a double open cubane, with one face of an Ln₁Na₂O₄ open cubane capped by an additional Ln₁O₂ layer. Clusters 1–3 show extremely high activity for the polymerization of ε-caprolactone (ε-CL) and trimethylene carbonate (TMC). The reactivity is much higher than those found for the monometallic alkoxides lanthanide complexes previously reported. The dependence of catalytic activity on lanthanide metals is observed: Yb ≈ Y < Sm for ε-CL and Yb < Y < Sm for TMC. The polymers obtained with these clusters all show a unimodal molecular weight distribution with moderate molecular weight distributions (M_w/M_n = 1.4–1.7), indicating that clusters 1–3 can really be used as single-component catalysts. The bimetallic cooperation and the coordination–insertion mechanism were proposed.