Application of ketenes to well‐defined polyester synthesis. II. Synthesis of reactive polyester by living anionic polymerization of (4‐halophenyl)ethylketene

Novel ketenes, (4‐chlorophenyl)ethylketene and (4‐bromophenyl)ethylketene, were synthesized by dehydrochlorination of 2‐(4‐halophenyl)butanoyl chlorides, and their anionic polymerizations by lithium (4‐methoxyphenoxide) in tetrahydrofuran at ?20 °C were carried out to afford the corresponding polyesters with narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight < 1.3) quantitatively. Polymerizations with various feed ratios afforded the corresponding polyesters with predictable molecular weights and narrow molecular weight distributions. Kinetic studies of the polymerizations at ?78 °C revealed that the polymerization rates were apparently larger than that of ethylphenylketene, which is considered to be responsible for the enhanced electrophilicities of the monomers via the introduction of electron‐negative halogen atoms. Monomer conversion agreed with the first‐order kinetic equation. These results strongly support the living mechanism of this polymerization. The obtained polyesters were modified by a palladium‐catalyzed coupling reaction of the side‐chain 4‐halophenyl group with 4‐methoxyphenylboronic acid, demonstrating their potential as reactive polymers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2093–2102, 2001     

α-亚甲基-β-丁内酯的区域选择性聚合:合成线形与环状聚酯

设计不同的催化体系或引发剂实现了α-亚甲基-β-丁内酯(MβBL)单体的区域选择性聚合,合成不同拓扑结构的聚酯.选用偶氮二异丁腈(AIBN)自由基引发剂,选择性聚合MβBL的α位上亚乙烯基双键,形成线形含有四元环内酯单元的聚酯.使用SalenAlCH3金属配合物催化剂,区域选择性在MβBL的酰-氧键断裂,生成双键保留以间同结构为主的结晶性线形聚酯.有机强碱是MβBL的高效开环聚合催化剂,获得以酰-氧键断裂为主的线形聚酯.而使用简单碘化钠催化MβBL开环聚合,形成以烷-氧键断裂为主的结晶性环状聚酯.     

Triazabicyclodecene: a simple bifunctional organocatalyst for acyl transfer and ring-opening polymerization of cyclic esters

1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) is an effective organocatalyst for acyl transfer as well as the ring-opening polymerization of cyclic esters. Its high activity is attributed to its ability to simultaneously activate both esters and alcohols, as demonstrated in a model reaction. This unique mechanism makes TBD a remarkably simple example of a bifunctional catalyst. The simplicity of the reaction conditions, the ready commercial availability of the catalyst, and its high activity provide an accessible methodology to allow future studies of tailor-made polyesters.     

Iterative tandem catalysis of secondary diols and diesters to chiral polyesters

The well-known dynamic kinetic resolution of secondary alcohols and esters was extended to secondary diols and diesters to afford chiral polyesters. This process is an example of iterative tandem catalysis (ITC), a polymerization method where the concurrent action of two fundamentally different catalysts is required to achieve chain growth. In order to procure chiral polyesters of high enantiomeric excess value (ee) and good molecular weight, the catalysts employed need to be complementary and compatible during the polymerization reaction. We here show that Shvo's catalyst and Novozym 435 fulfil these requirements. The optimal polymerization conditions of 1,1'-(1,3-phenylene) diethanol (1,3-diol) and diisopropyl adipate required 2 mol% Shvo's catalyst and 12 mg Novozym 435 per mmol alcohol group in the presence of 0.5 M 2,4-dimethyl-3-pentanol as the hydrogen donor. With these conditions, chiral polyesters were obtained with peak molecular weights up to 15 kDa, an ee value up to 99% and with 1-3 % ketone end groups. Also with the structural isomer, 1,4-diol, a chiral polyester was obtained, albeit with lower molecular weight (8.3 kDa) and slightly lower ee (94%). Aliphatic secondary diols also resulted in enantio-enriched polymers but at most an ee of 46 % was obtained with molecular weights in the range of 3.3-3.7 kDa. This low ee originates from the intrinsic low enantioselectivity of Novozym 435 for this type of secondary aliphatic diols. The results presented here show that ITC can be applied to procure chiral polyesters with good molecular weight and high ee from optically inactive AA-BB type monomers.     

A class of azocarbazole-based carboxylates: High-efficiency ionic unimolecular photobase generators for thiol-epoxy click polymerization under blue light

Two new unimolecular azocarbazole-based visible photobase generators (Ac-C-Base) with different strong bases such as 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) and 1,1,3,3-tetramethylguanidine (TMG) as the potential active species were prepared. Their structures were confirmed by ¹H NMR, ¹³C NMR, and HR-MS. According to the photolysis and EPR results, Ac-C-Base could generate free radicals and strong bases simultaneously through the photodecarboxylation mechanism under 455 nm LED irradiation. Thus they can effectively catalyze the thiol-epoxy polymerization without post exposure baking under light exposure. In addition, the Ac-C-TBD containing a stronger base shows a faster polymerization rate and higher epoxy conversion.     

Experimental and computational studies of ring‐opening polymerization of ethylene brassylate macrolactone and copolymerization with ε‐caprolactone and TBD‐guanidine organic catalyst

The ring‐opening polymerization (ROP) of ethylene brassylate, catalyzed by the cyclic guanidine 1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene (TBD) is reported. Several experimental parameters were evaluated for bulk ROP process and polyesters, resulting in molecular weights between 3 and 15 kg mol^?1. End‐group analysis by ¹H nuclear magnetic resonnance (NMR) and matrix assisted laser desorption ionization time of flight computational studies supports the dual behavior of TBD, which can act as both a catalyst and initiator of the polymerization process. Under optimum conditions, semicrystalline poly(ethylene brassylate‐co‐ε‐caprolactone) random copolymers were synthesized. Depending on the comonomer content, our results showed a range of melting temperatures between 39 and 69 °C. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 552–561     

Study of the carbon dioxide chemical fixation—activation by guanidines

Fixation of CO₂ is one of the most important priorities of the scientific community dedicated to reduce global warming. In this work, we propose new methods for the fixation of CO₂ using the guanidine bases tetramethylguanidine (TMG) and 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]-pyrimidine (TBD). In order to understand the reactions occurring during the CO₂ fixation and release processes, we employed several experimental methods, including solution and solid-state NMR, FTIR, and coupled TGA-FTIR. Quantum mechanical NMR calculations were also carried out. Based on the results obtained, we concluded that CO₂ fixation with both TMG and TBD guanidines is a kinetically reversible process, and the corresponding fixation products have proved to be useful as transcarboxylating compounds. Afterward, CO₂ thermal releasing from this fixation product with TBD was found to be an interesting process for CO₂ capture and isolation purposes.     

Synthesis and reactions of a poly(methacrylate) from an optically active amino alcohol

Synthesis and radical polymerization of a novel optically active methacrylate, (S)–2–tert–butoxycarbonylamino–3–phenylpropyl methacrylate (MA–F–BOC), were examined. MA–F–BOC was synthesized from methacrylic acid and N–protected (L)–phenylalaninol. Radical polymerization of MA–F–BOC quantitatively afforded the corresponding polymethacrylate with a relatively high molecular weight. Radical copolymerizations of MA–F–BOC were carried out with styrene and acrylamide to afford the copolymers. Radical polymerization of MA–F–BOC in the presence of n–butanethiol afforded the oligomers, whose degrees of polymerizations were 3.3–8.0. The BOC group was completely cloven with HBr to afford the corresponding optically active polymeric amine quantitatively. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 1981–1986, 1998     

Lactone Polymerization and Polymer Properties

Abstract

The polymerization of lactones provides a facile route to polyesters that is unimpeded by the long reaction cycles and elevated temperatures inherent in the condensation of hydroxyl and acid functional groups. Depending on the structure of the lactone monomer, catalyst/initiator systems are known which allow preparation of extremely high molecular weight polyesters of low polydispersity. In addition to obtaining high molecular weight polyesters in relatively short reaction cycles and at moderate temperature, lactone polymerization allows careful control of polymer end groups through proper selection of the initiating species. The type of end group plays an important role in both the thermal stability and hydrolytic stability of the resulting polyester. This study reviews and updates the field of lactone polymerization with specific emphasis on the chemistry and Theological     

Synthesis of a well-defined polybromostyrene by living radical polymerization with a nitroxyl radical

Radical polymerization of p-bromostyrene was investigated with benzoyl peroxide (BPO) as an initiator in the presence of 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MTEMPO). The polymerization was performed in bulk for 3.5 h at 95°C and then continued for another 48 h at 125°C to afford the corresponding polybromostyrene with a narrow molecular weight distribution in high yield. ¹H NMR study revealed that the polymer obtained had BPO and MTEMPO moieties at its head and tail, respectively. It was confirmed that the polymerization proceeded in accordance with living mechanism, because the molecular weight linearly increased with an increase of the conversion, and it was directly proportional to the reciprocal of the initial concentration of BPO. Furthermore, the polystyrene obtained in the present study could quantitatively act as the initiator for the polymerization of p-bromostyrene in the living radical manner to afford the corresponding block copolymer, and vice versa. © 1996 John Wiley & Sons, Inc.     

Mutation effects of a conserved alanine (Ala510) in type I polyhydroxyalkanoate synthase from Ralstonia eutropha on polyester biosynthesis

Type I polyhydroxyalkanoate (PHA) synthases, as represented by Ralstonia eutropha enzyme (PhaC(Re)), have narrow substrate specificity toward (R)-3-hydroxyacyl-coenzyme A with acyl chain length of C3-C5 to yield PHA polyesters. In this study, saturation point mutagenesis of a highly conserved alanine at position 510 (A510) in PhaC(Re) was carried out to investigate the effects on the polymerization activity and the substrate specificity for in vivo PHA biosynthesis in bacterial cells. A series of saturation mutants were first applied for poly[(R)-3-hydroxybutyrate] homopolymer synthesis in Escherichia coli and R. eutropha PHB(-)4 (PHA negative mutant) cells to assess the polymerization activity. All mutants showed quantitatively similar polymerization activities when R. eutropha PHB(-)4 was used for assay, whereas several mutants such as A510P showed low activities in E. coli. Further analysis has revealed that majority of mutants synthesize polyesters with higher molecular weights than the wild-type. In particular, substitution by acidic amino acids, A510D(E), led to remarkable increases in molecular weights. Subsequently, PHA copolymer synthesis from dodecanoate (C12 fatty acid) was examined. The copolymer compositions were varied depending on the mutants used. Significant increased fractions of long monomer units (C6 and C8) in PHA copolymers were observed for three mutants [A510M(Q,C)]. From these results, the mutations at this potion are beneficial to change the molecular weight of polyesters and the substrate specificity of PhaC(Re). Molecular weight distributions of PHA polymers synthesized by the wild-type enzyme (PhaC(Re)) and its mutants.     

Application of ketenes to well-defined polyester synthesis. III. Living anionic polymerization of ethyl(4-methoxyphenyl)ketene—Development of polyester having masked phenol side chain

A novel ketene, ethyl(4-methoxyphenyl)ketene (EMPK), was synthesized by the dehydrochlorination of 2-(4-methoxyphenyl)butanoyl chloride. The anionic polymerizations of EMPK by butyllithium in tetrahydrofuran at −20 °C were carried out with a varying feed ratio to give the corresponding polyesters having predictable molecular weights and narrow molecular weight distributions, quantitatively. The selective formation of the polyester was confirmed by IR analysis, and the reductive degradation of the polymer was supported by lithium–aluminium hydride. The second feed of the monomer (after the first stage of polymerization) resulted in the formation of the polymer with the expectedly increased molecular weight and low polydispersity to strongly support the living mechanism of this polymerization. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1596–1600, 2001     

Synthesis and Characterization of Hybrid Biopolymers of L-lactic Acid and 2-Pyrone-4,6-dicarboxylic Acid

Copolymers of L-lactic acid (LA) and 2-pyrone-4,6-dicarboxylic acid (PDC), a chemically stable metabolic intermediate of lignin, were prepared by dehydrated polycondensation based on stepwise oligomerization followed by post-polymerization in vacuo. When the polymerization was performed in the presence of methanesulfonic acid as a catalyst, the molecular weights of the resulting copolymers were sufficiently high. Furthermore, expansion of the polymeric surface area was found to be an important factor in facilitating dehydration and thereby producing high molecular weight polymers. PDC feed ratio significantly affected the molecular weight because of the different polymerization capability from LA. Relationship between the PDC feed ratio and the molecular weight of the resulting polyesters was for the first time demonstrated quantitatively. The obtained copolymers were characterized by ¹H- and ¹³C-NMR, IR, and thermal analysis. The high molecular weight copolymers possessed the higher decomposition temperatures than PLLA and their fusible temperature ranges were reasonably expanded.     

软段结构对聚氨酯性能影响的研究

用熔融缩聚法俣成了己二酸系和己二酸／芳香二酸混合系两个系列的聚酯；同溶液一步法将部分聚酯与ＭＤＩ反应，形成一系列聚酯型氨酯，以化学分析，ＶＰＯ，ＩＲ，ＤＳＣ，ＷＡＸＤ，力学拉伸等手段对聚酯和聚氨酯进行了表征；讨论了软段聚酯的结构对聚氨酯的结晶性，耐热性，粘结性等性能的影响。     

Synthesis and characterization of biodegradable-cum-crosslinkable well-defined polyesters via chain-growth polycondensation in solid-liquid phase

Well-defined aliphatic polyesters, polyglycolide (PGA), polylactide (PLA) and their copolymers (PLGA) were prepared by chain-growth polycondensation of potassium 2-bromocarboxylates in solid-liquid phase. The polymerization proceeded in a living fashion without any side reactions. The degrees of polymerization (D_p) of polyesters was in agreement with the feed ratio of monomer to initiator. The polymer, which was only composed of heptamer, octamer and nonamer, possessed a narrow molecular weight distribution. Furthermore, the end groups of polymers, such as allyl and phenyl units, were directly yielded during the polymerization for the further modifying and crosslinking. The synthesized polyesters with allyl end groups were successfully crosslinked, and the products possessed biodegradability in phosphate buffer solution at 37 °C.     

Biodegradable materials by reactive extrusion: from catalyzed polymerization to functionalization and blend compatibilization

This contribution aims at reviewing how reactive extrusion (REx) technique can participate in the design and development of biodegradable polymeric materials more particularly based on aliphatic polyesters issued from both renewable (agrochemical) and fossil (petrochemical) resources. On one side, REx will be approached for producing in a continuous way biodegradable aliphatic polyesters by ring-opening polymerization of lactones. Tin and aluminum-based catalysts will be considered for quantitatively converting the cyclic monomer in high molecular weight polyester chains within residence time of a few minutes only. On the other hand, such polyesters will undergo various chemical modifications again performed by REx. Self-branching reactions will be investigated in order to compensate the characteristic molecular weight reduction of the polyester chains as triggered by hydrolysis and/or transesterification side-reactions. Controlled functionalization reactions by maleic anhydride treatment will be studied as well. Finally biodegradable composite materials will be produced by REx and will rely upon the interface compatibilization between the polyester matrix and natural fillers such as starch granules or talc microparticles. To cite this article: J.-M. Raquez, et al., C. R. Chimie 9 (2006).     

Synthesis of poly(hydroxyurethane) from 5-membered cyclic carbonate under mild conditions in the presence of bicyclic guanidine and their reaction process

A series of amines are applied as catalysts in the aminolysis reactions of five-membered cyclic carbonate (5CC). Kinetic results display that TBD, which has a guanidine structure, exhibits the best catalytic efficacy and the reaction rate constant is about 100 times higher than the blank system without catalyst. The reaction medium, NMP is found to be as both solvent and promoter in the aminolysis of 5CC. Finally, with TBD and NMP as catalyst and solvent, respectively, the polymerization of bis-functional 5CC (B5CC) and 1, 6-diaminohexane can proceed almost 100% at room temperature in less than 4 h to obtain poly(hydroxyurethane)s (PHUs) with moderate molecular weight.     

Macromolecular engineering of polylactones and polylactides. X. Selective end-functionalization of poly(D,L)-lactide

Functional aluminum alkoxides, such as Et_3–pAl(O? CH₂? X)_p, where p = 1,3 and X = a functional group, are very effective initiators for the (D, L)-lactide polymerization in toluene at 70°C. The coordination-insertion type of polymerization is living. Linear polyesters of a predictable molecular weight and a narrow molecular weight distribution are obtained within the period of time required for the total monomer conversion. The functional group (X) associated with the active alkoxy group of the initiator is selectively and quantitatively attached to one chain end, whereas the second end group is systematically a hydroxyl function resulting from the hydrolysis of the living growing site. Asymmetric telechelic polylactides are thus obtained in a perfectly controlled way. A kinetic study has shown that the polymerization is first order in both the monomer and initiator. © 1993 John Wiley & Sons, Inc.     

Novel lipase-catalyzed ring-opening copolymerization of oxiranes and succinic anhydride forming polyesters bearing functional groups

Oxiranes, such as glycidyl phenyl ether (GPE) and benzyl glycidate (BG), were copolymerized with succinic anhydride (SA) by lipase at a temperature between 60 and 80°C to yield the corresponding polyesters bearing carboxyl or phenyl groups. Bulk polymerization, especially at the temperature of 80°C, and preferably using porcine pancreatic lipase gave biodegradable polyesters with a molecular weight greater than 5000.     

FTIR-ATR Monitoring and SEC/RI/MALLS Characterization of ATRP Synthesized Hyperbranched Polyacrylates

This work reports the synthesis at 1 L scale of hyperbranched polyacrylates based upon acrylate/diacrylate monomers such as n-butyl acrylate (nBA)/1,6-hexanediol diacrylate (HDDA) and using atom transfer radical polymerization (ATRP). A FTIR-ATR immersion probe was used to monitor the polymerization reaction. The dynamics of the build-up of polymer structure was studied by off-line analysis of samples at different reaction times by size exclusion chromatography (SEC) with detection of refractive index (RI) and multi-angle laser light scattering (MALLS) signals, leading to molecular weight distribution and z-average radius of gyration. Kinetic measurements and observed parameters of the molecular architecture are compared with theoretical predictions which can be used to design new synthesis strategies to improve the homogeneity of hyperbranched polymers. Another goal of this study was elucidating the impact on polymerization of secondary reactions such as intramolecular cyclizations. For comparison purposes, FRP (conventional radical polymerization) of the same monomers is also considered.