Modification of polypeptide materials by Thiol-X chemistry

Thiol-X chemistry has proven to be a valuable toolbox for modification of peptides, proteins, monomers, and polymers. Recently, this has become especially true for the modification of polypeptides (monomers or polymers), which has resulted in a plethora of novel polymers and materials. With this in mind, this highlight focuses on the recent literature concerning the modification of polypeptides by the use of thiol-X chemistry, in particular to synthetic polypeptides either at the monomer or polymer stage modified by thiol-ene, -Michael addition, and -yne chemistries.     

Accelerated pressure synthesis and characterization of 2-oxazoline block copolymers

The cationic ring-opening polymerization of 2-oxazolines in acetonitrile was investigated under pressure conditions utilizing methyl tosylate as initiator of which the single crystal X-ray structure is described as well. The polymerization kinetics were studied and compared with previously reported microwave-assisted pressure polymerizations. Moreover, a series of block copolymers was synthesized in an automated parallel synthesis robot utilizing this pressure polymerization method. The resulting block copolymers were characterized with both differential scanning calorimetry and contact angle measurements to determine the effect of copolymer composition on glass transition temperature, melting point and surface energy. Atomic force microscopy was applied to further investigate the possible phase separation.     

One-pot synthesis of poly(triazole-graft-caprolactone) via ring-opening polymerization combined with click chemistry as a novel strategy for graft copolymers

The one-pot construction of polytriazole grafted with poly(ε-caprolactone) via the polymerization of 4-azido-1-(prop-2-yn-1-yloxy)butan-2-ol (N₃hydroxypropargyl) and ε-caprolactone monomers is reported. For this purpose, a click reaction and ring-opening polymerization (ROP) were combined and carried out simultaneously. N₃hydroxypropargyl served as both the ROP initiator and a monomer for the click polymerization. Thus, an in situ “grafting-through and from” strategy was established in one pot. CuBr and Sn(Oct)₂ were utilized as dual catalysts, and the polymerization reactions were carried out at 120 °C under a N₂ atmosphere.     

A new strategy for the one-step synthesis of block copolymers through simultaneous free radical and ring opening polymerizations using a dual-functional initiator

Block copolymers are fascinating and complex materials that have been used in a range of diverse scientific and technological capacities. We demonstrate that a single one-step approach based on dual simultaneous polymerizations is a viable technique for the synthesis of a wide range of block copolymers by combining two dissimilar polymerization systems and using a dual-functional initiator. The main advantage of this methodology is that a simple, one-step, and simultaneous polymerization occurs in the bulk, which makes this process very attractive from both industrial and academic points of view. We plan to study the reaction kinetics and evaluate how well the ring opening catalyst [in this case, Sn(oct)₂] works under reverse ATRP conditions.     

Highly branched benzoxazine monomer based on cyclotriphosphazene: Synthesis and properties of the monomer and polybenzoxazines

A hyperbranched organic-inorganic hybrid benzoxazine monomer based on cyclotriphosphazene (CP) has been synthesized, which possesses six organic benzoxazine moieties distributed on the inorganic ring of CP. The high molecular weight (1491 g/mol) monomer showed excellent solubility in common organic solvents. Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) were used to study the thermal ring-opening polymerization reaction of the novel benzoxazine monomer. FT-IR spectrum implied that the characteristic absorption peaks of the benzoxazine ring disappeared completely after curing at 240 °C for 1 h, which illustrated that the completion of polymerization reaction. DSC plots indicated that the melting point of the new monomer was 77 °C and an exothermic peak was 225 °C owing to the ring-opening polymerization of the monomer. Due to its highly steric crosslinking structure with rigid and thermal stable inorganic CP as the core, the polybenzoxazine based on the new monomer showed excellent thermal stability and mechanic properties. The char yield of the polymer at 850 °C was 66.9% in nitrogen, and the T_g of the polybenzoxazine was 152 °C.     

A novel binder suitable for cationic electrodeposition coatings based on a non-isocyanate chemistry

A non-polyisocyanate resin system that can be applied to cationic electrodeposition (CED) paint has been developed. Most of the compositions of binders currently on the market as CED coatings are composed of modified epoxy resins and blocked polyisocyanates, their crosslinking essentially being polyurethane or polyurea formation. This report deals with a new resin system of which crosslinking is based on a ring-opening/etherification reaction between epoxy groups and hydroxyl groups. The ring-opening addition reaction has very low emissions during the baking process. However, it is difficult to attain a compromise between satisfactory reactivity at elevated temperatures and stability in aqueous composition. By a series of careful investigations, we have established the composition of CED coatings that are sufficiently stable and can be satisfactorily cured. The CED paint formulated on this resin system has such desirable properties as low weight loss upon baking, outstanding weatherability, and excellent chipping resistance. Other characteristics are comparable to existing polyisocyanate based CED coatings.     

新型聚硅氧烷嵌段共聚物的合成研究进展

聚硅氧烷作为一种有机硅高聚物,可通过嵌段共聚进行相应的化学改性。综述了国内外新型聚硅氧烷嵌段共聚物的研究进展,主要对纯聚硅氧烷嵌段型、聚醚型、聚烯烃型和聚氨酯型进行了叙述,并对其应用前景进行了展望。     

Diblock copolymers with an amorphous, high glass transition temperature, organometallic block: synthesis, characterisation and self-assembly of polystyrene-b-poly(ferrocenylisopropylmethylsilane) in the bulk state

Living anionic ring-opening polymerisation of isopropylmethylsila[1]ferrocenophane yields poly(ferrocenylisopropylmethylsilane) (PFiPMS) with controlled molecular weights and narrow polydispersities up to M_n = ca. 20,000 Da. Polystyrene-b-poly(ferrocenylisopropylmethylsilane) (PS-b-PFiPMS) diblock copolymers have been prepared via sequential living anionic polymerisation. These materials are examples of diblock copolymers with an amorphous, organometallic block with a glass transition temperature (T_g) above room temperature (60 °C). High molecular weight diblock copolymers (M_n = 42,000–51,000 Da) were targeted with low polydispersities (PDI = 1.1). As both blocks are amorphous, these materials self-assemble into predictable morphologies in the bulk state with well-ordered nanodomains.     

Acrylic copolymers crosslinked by click chemistry: Some aspects of synthesis,curing, and crosslinking

Acrylic polymers bearing pendant azide and propargyl groups were synthesized by chemical transformation of epoxy‐ and carboxylic functional acrylic precursor polymers and were characterized. These copolymers were crosslinked by reacting them in the presence of Cu(I) catalyst via the azide–alkyne click reaction leading to triazole networks. Influence of catalyst concentration on the crosslinking cure kinetics was investigated, and the activation parameters were evaluated. The activation energy decreased from 90 kJ mol^?1 to 25 kJ mol^?1 on catalyzing the cure reaction as estimated by Ozawa method. Differential scanning calorimetric analysis indicated thermal decomposition of the residual azide groups at around 200–220°C, which was catalyzed by Cu(I) with associated activation energy of 130–94 kJ mol^?1. Isothermal cure reaction and decomposition of the azide groups were predicted using these parameters. Estimation of crosslink density by solvent swelling and dynamic mechanical analyses showed a normal crosslinking behavior. While the solvent swelling rate and the equilibrium swelling decreased, the front factor and diffusion coefficient of swelling showed a transition from non‐Fickian to Fickian as the triazole concentration increased in the network. The click reaction offered an alternate means to crosslink acrylate polymers. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1289‐1300, 2013     

Synthesis, characterization and aggregation behavior of block copolymers containing a polyisocyanopeptide segment

Following up on previous preliminary communications the synthesis of a series of block copolymers by applying amine end-capped polymers as initiators for the nickel(II) catalyzed polymerization of isocyanides is reported. Using a polystyrene derivative as the initiator, superamphiphiles containing a hydrophobic polystyrene tail and a charged helical polyisocyanide headgroup were prepared. Under proper conditions these superamphiphiles self-assembled in water to give a variety of aggregate morphologies, among which are superhelical architectures. Initiators derived from carbosilane dendritic wedges gave block copolymers with a unique combination of structural elements, i.e. a flexible dendritic block and a rigid polyisocyanide block. Block copolymers derived from the 3rd generation dendrimers form well-defined micellar aggregates in the presence of Ag⁺ ions. These aggregates have been used to construct nanoarrays of metallic silver.     

新型吡唑基吡啶衍生物的合成及催化Suzuki偶联反应

以4-苯基苯酚和4-叔丁基苯酚为原料设计合成杯芳烃片段桥连的吡唑基吡啶衍生物L1、L2,并采用1H NMR、13C NMR对其结构进行表征。结果表明,化合物L1作为配体,V (DMF)∶V (水)=2:1为溶剂,在80℃时对钯催化Suzuki偶联反应有良好的促进作用。     

New azo-chromophore-containing multiblock poly(butadiene)s synthesized by the combination of ring-opening metathesis polymerization and click chemistry

A combination of ring-opening metathesis polymerization (ROMP) and click chemistry approach was utilized for the first time in preparation of multiblock copolymers. The dibromo-functionalized telechelic poly(butadiene) (PBD) was synthesized firstly by ROMP of 1,5-cyclooctadiene in the presence of a symmetrical difunctional chain transfer agent and transformed into diazido-telechelic PBD, which was then reacted with a dialkynyl-containing azobenzene chromophore via click reaction, producing novel multiblock PBDs collected by azobenzene groups and newly formed triazole moieties. The monomer and polymer were characterized by IR, UV-vis, LC/MS, and NMR techniques. The produced multiblock copolymers have molecular weights within 13.3 and 57.8 kDa, and their polydispersity indices ranging from 1.98 to 2.38 by gel permeation chromatography measurement. The multiblock PBDs containing azo chromophores and triazole moieties with or without hydrogen-bonding interreaction with 4,4′-dihydroxybiphenyl molecule exhibited different photoisomerization efficiency from trans to cis as observation in UV-vis spectroscopy. The morphologies of multiblock PBDs were also investigated by atom force microscopy.     

Preparation and evaluation of novel amphiphilic glycopeptide block copolymers as carriers for controlled drug release

In the present study we describe a synthesis and self-assembly and an in vitro evaluation of a kind of novel amphiphilic glycopeptide block copolymers as carriers for controlled drug release. Initially, an amphiphilic ABA triblock copolymer comprising polytetrahydrofuran (PTHF) as a central hydrophobic block flanked by poly(l-lysine)s (PLLs) as outer hydrophilic blocks was synthesized through the ring-opening polymerization of ?-benzyloxycarbonyl-l-lysine N-carboxyanhydride with a distal amine-terminated PTHF as a macroinitiator, followed by removal of the protecting group. Afterwards the resulting triblock copolymer was allowed to react with d-gluconolactone and lactobionolactone in the varying feeding ratios in the presence of diisopropylethylamine leading to the target glycopeptide block copolymers with high yields. They were found to easily self-assemble into nano-sized aggregates in water. The critical aggregation concentrations (CACs) were assessed by fluorescence measurement with N-phenyl-1-naphthylamine employed as a molecular probe. The particle sizes of the aggregates before and after doxorubicin loading were determined by dynamic light scattering (DLS) and the aggregate morphologies were evidenced by transmission electron microscopy (TEM) measurements. Finally, the in vitro doxorubicin loading capacity and release behavior were investigated with these glycopeptide copolymers as carriers for controlled release.     

β-Enaminoesters as building blocks in heterocyclic synthesis. A novel synthesis of fused azines by using blaise reaction as a key step

Ethyl bromoacetate 4 reacts with nitriles in the presence of activated zinc dust to afford the β-enaminoesters 7 and 19 . Compounds 7 and 19 show high reactivity towards a variety of reagents to give polyfunctional heterocyclic compounds. For example, the enaminoesters 7 and 19 react with benzaldehyde to give the 1,4 dihydropyridine derivatives 9 and 20 respectively. Isothiocyanates 24 (R = Ph, OEt) added to 19 to furnish pyrimidine-thiones 26 and 27 respectively. Structures and conceivable mechanisms are discussed     

丙烯腈嵌段共聚物的合成及其自组装研究进展

综述了含聚丙烯腈(PAN)嵌段共聚物的合成方法及其在溶液中的自组装技术。对常用的活性自由基聚合方法,如原子转移自由基聚合(ATRP)、可逆加成断裂链转移(RAFT)聚合、氮氧自由基聚合(NMP)以及钴调介自由基聚合(CMRP)等方面的研究进行了总结,同时对PAN类嵌段共聚物在溶液中的自组装技术进行了概括。最后提出了现有技术存在的问题,并对其今后发展方向进行了展望。     

组合化学液相合成进展

综述了组合化学中液相合成技术的最新进展。     

Study on a novel catalytic reaction and its mechanism for CF3I synthesis

A novel vapor phase production process for CF₃I was successfully developed for the reaction between CHF₃ with I₂ in the presence of a unique catalyst. The most effective catalyst system for this reaction was found to be alkali metal salts which were supported on an activated carbon carrier. A consideration of the reaction mechanism suggests that the reaction proceeds via CF₂ carbenes formed on the catalyst surface as intermediates, followed by carbene disproportionation to CF₃ radicals, followed by reaction with I₂ to give CF₃I.     

Using heavy ethers as structure modifiers in the synthesis of SBS block copolymers in cyclohexane

Heavy ethers—diethoxyethane (DIOXO) and triethylorthoacetate (TEOA)—were evaluated and compared with monoethers such as tetrahydrofuran (THF) and diethylether (DEE) as structure modifiers during the synthesis of linear styrene-butadiene block copolymers of polyA-block-polyB-block-polyA type (SBS). A smaller amount of a heavy ether than a monoether was needed to achieve the same targeted content of the 1,2-polybutadiene (vinyl) microstructure. The vinyl content increased from 10 to 71% with increase in the amount of TEOA from 10 ppm to 1 wt %, while the trans-1,4 and cis-1,4 units decreased. Similarly, increasing the amount of DIOXO from 10 ppm to 1 wt % increased the vinyl content from 17 to 89%. TEOA, 300 ppm, or DIOXO, 50 ppm, were suggested for making an SBS copolymer with a targeted 40% vinyl content. The addition of heavy ethers as structure modifiers also increased the rates of polymerization for both styrene and butadiene. Among all ethers, DIOXO enhanced the rate of butadiene polymerization the most, whereas TEOA caused the highest rate of styrene polymerization. Heavy ethers accelerated the rates of polymerization more than did monoethers. Furthermore, for an SBS polymer synthesized via a sequential method, the addition of heavy ethers enhanced the crossover efficiency, resulting in a narrower molecular weight distribution with a lower polydispersity. For an SBS polymer made via a coupling method, the coupling efficiency decreased and varied with the type of the coupling agent used. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2543–2560, 1997