Synthesis of PMMA‐b‐PBA block copolymer in homogeneous and miniemulsion systems by DPE controlled radical polymerization

In this research, poly(methyl methacrylate)‐b‐poly(butyl acrylate) (PMMA‐b‐PBA) block copolymers were prepared by 1,1‐diphenylethene (DPE) controlled radical polymerization in homogeneous and miniemulsion systems. First, monomer methyl methacrylate (MMA), initiator 2,2′‐azobisisobutyronitrile (AIBN) and a control agent DPE were bulk polymerized to form the DPE‐containing PMMA macroinitiator. Then the DPE‐containing PMMA was heated in the presence of a second monomer BA, the block copolymer was synthesized successfully. The effects of solvent and polymerization methods (homogeneous polymerization or miniemulsion polymerization) on the reaction rate, controlled living character, molecular weight (M_n) and molecular weight distribution (PDI) of polymers throughout the polymerization were studied and discussed. The results showed that, increasing the amounts of solvent reduced the reaction rate and viscosity of the polymerization system. It allowed more activation–deactivation cycles to occur at a given conversion thus better controlled living character and narrower molecular weight distribution of polymers were demonstrated throughout the polymerization. Furthermore, the polymerization carried out in miniemulsion system exhibited higher reaction rate and better controlled living character than those in homogeneous system. It was attributed to the compartmentalization of growing radicals and the enhanced deactivation reaction of DPE controlled radical polymerization in miniemulsified droplets. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4435–4445, 2009     

结构明确的梳形支化聚合物的合成与表征

通过活性聚苯乙烯(PS)和聚异戊二烯(PI)负离子与含1,1-二苯基乙烯(DPE)侧基的聚苯乙烯(PSe)的偶联反应合成了结构明确的每个重复单元含一条侧链的梳形支化聚合物,其中,PSe是通过Sc单体的原子转移自由基聚合(ATRP)和Wittig反应制得的.用IR1、H-NMR、GPC和SLS等测试方法对所得梳形支化聚合物进行了详细表征,讨论了活性负离子链与PSe的DPE基团的配比对接枝率的影响.结果表明,活性负离子链与DPE基团的偶联反应是高效的,可以通过调节活性负离子链与DPE基团的加料比来控制接枝率.另外,还讨论了PSe和活性负离子链的分子量对接枝率的影响.结果表明,在实验范围内当活性负离子链过量时可获得几乎定量的接枝率.     

Synthesis and kinetic analysis of DPE controlled radical polymerization of MMA

The 1,1‐diphenylethene (DPE) controlled radical polymerization of methyl methacrylate was performed at 80 °C by using AIBN as an initiator and DPE as a control agent. It was found that the molecular weight of polymer remained constant with monomer conversion throughout the polymerization regardless of the amounts of DPE and initiator in formulation. To understand the result of constant molecular weight of living polymers in DPE controlled radical polymerization, a living kinetic model was established in this research to evaluate all the rate constants involved in the DPE mechanism. The rate constant k₂, corresponding to the reactivation reaction of the DPE capped dormant chains, was found to be very small at 80 °C (1 × 10^?5 s^?1), that accounted for the result of constant molecular weight of polymers throughout the polymerization, analogous to a traditional free radical polymerization system that polymer chains were terminated by chain transfer. The polydispersity index (PDI) of living polymers was well controlled <1.5. The low PDI of obtained living polymers was due to the fact that the rate of growing chains capped by DPE was comparable with the rate of propagation. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2009     

Electrospray ionization mass spectrometric study of the hydrolysis-polycondensation process of Sn(OBu(t))(4)

The oligomerization of Sn(OBu(t))(4) in the sol-gel process has been studied by several different analytical approaches. Electrospray ionization (ESI) mass spectrometry was highly effective in describing the first species produced by the hydrolysis-polycondensation reactions. M?ssbauer spectroscopy has elucidated the fast behavior of the hydrolytic oligomerization process, while calorimetric data have demonstrated the high enthalpy of the reaction in the presence of different solvents.     

Appraisal of an oligomerization behavior of unprotected carbohydrates induced by phosphorus reagent

In this article, a novel oligomerization behavior of unprotected monosaccharides was discovered in a one-pot reaction induced by phosphorus reagent at room temperature. The inherent characteristics of the oligomerization reaction were dissected in detail by mass spectrometry based method combined with NMR technology. It was found that the main glycosidic bonding pattern is (1→6) linkage with 66% regioselectivity for each step. The ratio of α-(1→6) and β-(1→6) glycosidic bonds formed is around 1:1. The reactivity of 1-OH group from aldoses and the driving force from penta-coordinated phosphorus intermediates are the two critical factors for the oligomerization, according to the monitoring experiments by ESI-MS and NMR. Besides, the oligomerization reaction has good compatibility for various aldoses and could expand to O-glycosylated modification of peptides in vitro. The above results will provide a novel enlightenment to develop more convenient and higher-efficient methods for the synthesis of oligosaccharide library.     

二苯乙烯对秸秆纤维素超临界乙醇裂解转化液化产物的影响

以1,1-二苯乙烯(DPE)为阻聚剂,采用高压反应釜对玉米秸秆纤维素进行超临界乙醇液化,探究DPE浓度(用量)和反应温度对纤维素裂解碎片转化成液化产物的影响。结果表明,DPE浓度增加,挥发分收率降低了25.4%,生物油收率增加了19.9%,收率最高达39.8%,纤维素转化率有所下降;反应温度升高,纤维素转化率迅速增加到85.5%,挥发分也急剧升高,生物油收率最高为34.6%。GC-MS结果显示,生物油主要包括酮类、酯类、烃类等平台化合物以及较多的联苯化合物。DPE浓度过高,结合大量的纤维素裂解片段(乙基、羟基、甲基、氢等)形成联苯类化合物产生较强的空间位阻效应,使得纤维素裂解及活性片段转化成平台化合物的反应受到抑制,两者之间是一个竞争过程;温度升高,乙醇自由基活性增强,其对纤维素裂解的促进作用逐渐超过DPE对纤维素裂解的抑制作用,平台化合物收率有所升高。     

Synthesis of a Novel Polyfunctional Anionic Macroinitiator from a Polyfunctional 1,1‐Diphenylethylene Agent

Summary: A polyfunctional 1,1‐diphenylethylene (DPE) agent was prepared by ring‐opening metathesis polymerization of a DPE‐functionalized norbornene monomer. Its reaction with sec‐butyllithium gave a novel polyfunctional anionic macroinitiator with one 1,1‐diarylalkyllithium initiation functionality per repeating unit. The significant applicability of this polyfunctional anionic macroinitiator was demonstrated by its excellent initiation efficiencies in anionic polymerization and a preparation of a graft copolymer with well‐controlled long and dense diblock grafts.

Preparation of a polyfunctional anionic macroinitiator based on ROMP and DPE chemistry.     

Successive Synthesis of Well-Defined Star-Branched Polymers by “Convergent” Iterative Methodology Using Core-Functionalized 3-Arm Star-Branched Polymer and a Specially Designed 1,1-Diphenylethylene Derivative

The synthesis of well-defined regular and miktoarm star-branched polymers by a convergent iterative methodology using core-functionalized 3-arm star-branched polymer with 1,1-diphenylethylene (DPE) moiety and a specially designed DPE derivative is described. The methodology involves the following two reaction steps in the entire iterative synthetic sequence: 1) a coupling reaction of a star-branched polymer having an anion at the core with a DPE derivative with two benzyl bromide moieties, 1-{4-[5,5-bis(3-bromomethylphenyl)-7-methylnonyl]phenyl}-1-phenylethylene, and 2) an addition reaction of the resulting core-DPE-functionalized star-branched polymer with sec-BuLi to convert the DPE moiety to a DPE-derived anion. The iterative synthetic sequence including these two reaction steps, 1) and 2), was repeated to successively synthesize star-branched polymers with more arms. Iteration of this synthetic sequence doubled the number of the arms in the star-branched polymer. With this methodology, 6-arm, 12-arm, and 14-arm regular star-branched polystyrenes as well as 6-arm A₂B₂C₂, A₄B₂, and 12-arm A₄B₄C₄ and A₈B₄ miktoarm star-branched polymers with well-defined structures have been successfully synthesized.     

A mass spectrometric investigation on the possible role of tryptophan and 7-hydroxytryptophan in melanogenesis

The activity of tyrosinase and peroxidase + H2O2 in promoting melanogenesis from tryptophan (Trp) and 7-hydroxytryptophan (7-HTP) has been investigated. The reaction samples have been drawn at different reaction times and analysed by MALDI mass spectrometry. The data obtained showed that tryptophan undergoes, under tyrosinase and peroxidase action, an oligomerization process mainly due to the reaction of anthranilic acid (AA) and Trp. However, analysing the UV and fluorescence data, it is seen that the oligomers cannot belong to the melanin pattern, but their possible role in melanogenesis is not to be excluded. Once it reacts with the two enzymes, 7-hydroxytryptophan leads to dark brown products, indicating its possible role in melanin production. In contrast to what was observed in the case of 5-hydroxytryptophan, for which oligomers were constituted by 5-hydroxytryptophan (5-HTP) and 5-hydroxytryptamine (5-HT) units, the MALDI data indicate a sharply different behaviour for 7-HTP. In fact, in the case of 5-hydroxytryptophan, oligomerization takes place through the formation of 5-hydroxytryptamine and the oligomerization products are due to mixed 5-HTP-5-HT oligomers. In the case of 7-hydroxytryptophan, the formation of 7-hydroxytryptamine (7-HT) is also observed, but it does not seem to play any role; the only oligomerization products formed are due to the reaction of 7-hydroxytryptophan and AA. The data so obtained indicate that 7-hydroxytryptophan acts like an effective melanin precursor in the presence of both tyrosinase and peroxidase + H2O2.     

Synthesis of short straight-chain alkylamine based hyperbranched nickel complexes and their catalytic performance of ethylene oligomerization

Short straight-chain alkylamine based hyperbranched molecules and their corresponding salicylaldimine nickel complexes have been synthesized in high yield and characterized by FTIR, ¹H-NMR and mass spectrometry. The optimal reaction parameters were determined under the catalytic system of methylaluminoxane (MAO) as co-catalyst and toluene as solvent. Under these conditions, the effect of catalyst structure, solvent and co-catalyst were determined. Upon activation of MAO in toluene, ethylene oligomerization products were homogeneous distribution of butene, hexene and octene with trace higher olefin. The same catalytic system under cyclohexane and methyl cyclohexane as solvent, however, produced majority of butene. Under the activation of EtAlCl₂, Et₂AlCl and EASC as co-catalyst in toluene, ethylene oligomerization reaction was tandem with Friedel-Crafts reaction in catalytic system.     

13C-NMR study of arylene–ether–ketone copolymers

The chemical microstructure of arylene–ether–ketone copolymers of terephthaloyl chloride (TCl), 1,4-diphenoxybenzene (DPB), and diphenyl ether (DPE) has been characterized by ¹³C-NMR. Copolymers synthesized via two Friedel–Crafts reaction have been investigated; the first reaction uses HF and BF₃ to catalyze polymerization, and the second uses LiCl to moderate the activity of the Lewis-acid catalyst, AlCl₃. The HF/BF₃ approach results in random copolymers, in which the TCI displays no preference in reacting with either DPB or DPE. The buffered AlCl₃ approach yields somewhat blocky copolymers, in which the DPB and DPE tend to segregate. The degree of segregation in these materials has been quantified by formulas for the number-average block lengths.     

An investigation on the role of 3-hydroxykynurenine in pigment formation by matrix-assisted laser desorption/ionization mass spectrometry

In order to investigate the role of tryptophan and its metabolites in biogenesis of melanins, a study on the enzymatic reaction of 3-hydroxykynurenine with tyrosinase and peroxidase was performed. The reaction at different pH values was monitored by sampling at different times, with ultrafiltration used before analysis by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). The data obtained in this way showed that oligomerization processes take place with both enzymes, but with different behaviour, also depending on pH. 3-Hydroxykynurenine in the presence of tyrosinase at pH 6.0 leads to formation of xanthommatin, and at pH 8.0 hydroxanthommatin is formed in the first step of the reaction followed by formation of black-brown pigments. In contrast, the formation of oligomerization products by peroxidase action is observed in high yields under both acidic and basic conditions; however, at pH 6.0, a more extensive oligomerization process is observed. Thus peroxidase is able to activate oligomerization analogous to that observed in the case of tyrosinase without depending on the variation of pH. Due to the early formation of decarboxylated hydroxykynurenine, hydroxanthommatin and decarboxylated hydroxanthommatin, the enzymatic reaction leads to mixed oligomers, which can be considered as precursors of new pathways in pigment production.     

Intracluster anionic oligomerization of acrylic ester molecules initiated by electron transfer from an alkali metal atom

Stabilities and intracluster reactions have been investigated by photoionization mass spectrometry for clusters composed of an alkali metal atom (M; Na and K) and acrylic ester molecules, CH(2)=CHCO(2)R, such as methyl acrylate (MA; R = CH(3)) and ethyl acrylate (EA; R = C(2)H(5)). The following two features are commonly observed in the photoionization mass spectra of M(CH(2)=CHCO(2)R)(n): (1) The ion with n = 3 is clearly observed as a magic number. (2) Fragmented cluster ions with the loss of ROH, [M(CH(2)=CHCO(2)R)(n) - ROH] are detected only for n = 3. These features are both explained by an intracluster oligomerization reaction initiated by electron transfer from the metal atoms. The magic number trimer is concluded to have the stable structure of cyclohexane derivatives as a result of oligomerization. The fragmentation reaction is explained by Dieckmann cyclization after anionic oligomerization to produce another isomer of the trimer. The intracluster electron transfer is also supported by theoretical calculation for Na(MA) based on density functional theory.     

Biocatalytic Synthesis of Two-Photon Active Resveratrol Oligomer

Resveratrol (3,5,4′ trihydroxy trans-stilbene) is a plant based phenolic compound. Enzymatic oligomerization of trans-resveratrol using horseradish peroxidase followed by characterization of the oligomer is presented. The oligomerization reaction was monitored using UV-Visible absorption and fluorescence spectroscopies. The oligomer exhibits strong two-photon-induced fluorescence. Computational modeling using spin-density calculations was performed to investigate the most probable reaction sites and the nature of products formed in the oligomerization process.     

Synthesis of well‐defined functionalized polymers and star branched polymers by means of living anionic polymerization using specially designed 1,1‐diphenylethylene derivatives

This article covers precise syntheses of well‐defined chain‐end and in‐chain functionalized polymers, multi‐functionalized polymers with a definite number of functional groups, star‐branched and graft polymers by recently developed methodologies using specially designed 1,1‐diphenylethylene (DPE) derivatives. The DPE derivatives include various substituted DPE derivatives with functional groups and their derivatives, DPE‐functionalized DPE derivatives, and well‐defined DPE‐functionalized macromonomers. The synthetic utility and importance of these DPE derivatives are described via such polymer syntheses.     

Fire and Forget! One‐Shot Synthesis and Characterization of Block‐Like Statistical Terpolymers via Living Anionic Polymerization

Diphenylethylene (DPE) is a monomer which has attracted significant interest from academia and industry both in terms of copolymerization kinetics and for the potential to extend and tune the range of glass transition temperatures accessible for DPE‐containing copolymers. DPE can undergo (co)polymerization with a variety of other monomers by living anionic polymerization but is incapable of forming a homopolymer due to steric hindrance. DPE, being a sterically bulky monomer, results in dramatic increases in the glass transition temperature (T_g) of resulting copolymers, with a perfectly alternating copolymer of styrene and DPE having a T_g of ~180 °C. Herein we report for the first time, the outcome of the statistical terpolymerization of butadiene, styrene, and DPE—a one‐pot, one‐shot, commercially scalable reaction using monomers of wide industrial importance. This extremely facile approach produces copolymers with a block‐like structure, which undergo microphase separation, possess a high T_g glassy “block” and are virtually indistinguishable from analogous block terpolymers made by the traditional sequential addition of monomers approach. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 382–394     

Synthetic applications of non-polymerizable monomers in living carbocationic polymerization

The foundation and methodology of using highly reactive but non-polymerizable monomers in living cationic polymerizations is introduced. The chemistry and kinetics of 1,1-diphenylethylene (DPE) addition to living polyisobutylene (PIB) in methyl chloride/n-hexanes 40/60 v/v at −80°C is reported. Monoaddition occurred even when large excess of 1,1-diphenylethylene was used. The methanol quenched polymer of the DPE capped PIB carried -OCH₃ functionality exclusively, suggesting that the diphenyl alkyl chain-ends are completely ionized, which was confirmed by conductivity studies. By in-situ functionalization using soft nucleophiles a variety of functional groups were obtained, most notably ester upon reaction with silyl ketene acetal. It was found that the diphenyl carbenium ion is an efficient initiating species for the polymerization of reactive monomers such as vinyl ethers and α-methylstyrene. The synthesis of PIB based block copolymers was accomplished by sequential monomer addition, using para-methylstyrene, α-methylstyrene or isobutyl vinyl ether as the second monomer. It involved capping with DPE, followed by tailoring the Lewis acidity to the reactivity of the second monomer by the addition of titanium(IV) alkoxide, by replacing the Lewis acid with a weaker one or by the use of a common ion salt. PIB-b-PMMA was obtained by the combination of living cationic and group transfer (GTP) polymerizations.     

UV固化超支化聚酯树脂的制备研究

以双季戊四醇（DPE）为超支化核心，与偏苯三酸酐（TMA）和甲基丙烯酸缩水甘油酯（GMA）反应合成了超支化聚酯树脂。偏苯三酸酐半酯化后产生羧基，羧基再与GMA中的环氧基反应提供UV固化性能。同时研究了温度、催化剂等因素对反应的影响。     

Synthesis of a novel centipede-like copolymer of styrene and methyl methacrylate

A well-defined,A2B-type,centipede-like copolymer of styrene and methyl methacrylate(PS-PS-PMMA) was synthesized by the combination of living anionic polymerization and atom transfer radical polym-erization(ATRP) . The synthetic approach involves the coupling reaction of polystyrene(PS) backbone bearing 1,1-diphenylethene(DPE) pendant groups,produced by ATRP and Wittig reaction,with living polystyryllithium(PSLi) ,and subsequent polymerization of the resulting 1,1-diphenylmethyl anions with methy methacrylate. The centipede-like copolymer was characterized by 1H NMR,IR,SEC,SLS,and DSC measurements.     

MALDI TOF mass study on oligomerization of Pd(OAc)2(L)2 (L = pyridine derivatives): relevance to Pd black formation in Pd-catalyzed air oxidation of alcohols

[reaction: see text] Oligomerization of Pd(OAc)2(L)2 (L = pyridine derivatives), a catalyst for the air oxidation of alcohols, is studied with MALDI TOF mass, using dithranol as the matrix. The degree of the Pd oligomerization is influenced by the pyridine ligands, and this ligand effect is similar to one observed for Pd black formation in the catalysis.