Polylactones. 10. Cationic polymerization of .delta.-valerolactone by means of alkylating reagents

Kricheldorf, Hans R.; Dunsing, Ruth; Serra, Àngels

doi:10.1021/ma00175a002

Cited by 34 publications

(17 citation statements)

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“…Fourthly, Bi triflate‐catalyzed polymerizations of εCL were conducted at 20 °C in bulk with monomer/catalyst/ ratios of 20 and 50 (not listed in Tables) and the virgin reaction products were subjected to 1 H NMR measurements. The characteristic signals of the cationic chain ends (formulated in Scheme ) were not detectable in contrast to methyl triflate‐initiated polymerizations of δ ‐valerolactone published previously 54. Furthermore, methyl ester end‐groups (structure Lb in Scheme ) are expected when a cationically polymerized poly(εCL) is precipitated into methanol, but methyl ester end groups were never observed.…”

Section: Resultsmentioning

confidence: 70%

“…The results presented in Figure 1 raise at first the questions if metal triflate catalyzed polymerizations involve a proton catalyzed cationic mechanism (Scheme ) or a kind of coordination‐insertion mechanism (Scheme and ). Characteristic for a true cationic mechanism, as it was elaborated by Penczek and co‐workers 52 and Kricheldorf et al,53, 54 is the cleavage of the O–alkyl bond in each growing step and the existence of a cationic end group. The following observations favor a coordination‐insertion mechanism.…”

Section: Resultsmentioning

confidence: 97%

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Bismuth‐Triflate‐Catalyzed Polymerizations of ε‐Caprolactone

Lahcini

Qayouh

Yashiro

et al. 2011

Macro Chemistry & Physics

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εCL was polymerized using the triflates of lanthanum, samarium, magnesium, aluminum, scandium, and bismuth as catalysts. Bismuth triflate proved to be extraordinarily reactive, and catalyzed polymerizations of εCL even at 20 °C. Adding DTBMP reduced the polymerization rate only slightly. Furthermore, no evidence of a cationic mechanism was found by end‐group analyses. Polymerization at 20 °C either in bulk or in solution only yielded polyesters of low or medium molecular weights ($\overline {M} _{{\rm n}} $ up to 30 000 Da). Yet addition of alcohols allowed for a proper control of molecular weight and end‐groups. Additionally, low catalyst concentrations and low temperature resulted in narrow molecular weight distributions and polylactones almost free of cyclic compounds.

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Section: Resultsmentioning

confidence: 70%

Section: Resultsmentioning

confidence: 97%

Bismuth‐Triflate‐Catalyzed Polymerizations of ε‐Caprolactone

Lahcini

Qayouh

Yashiro

et al. 2011

Macro Chemistry & Physics

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“…The strong Brønsted acids are only effective ROP catalysts for specific substrates, such as 1,3-dioxepan-2-one [147], and only several types of Brønsted and Lewis acids demonstrated the high efficiency in ROP of common cyclic esters, such as δVL, εCL, TMC, or LA. The ability of sulfonic acids [148][149][150][151][152][153][154][155][156][157][158][159], carboxylic acids [160][161][162][163], acidic phosphates [164][165][166][167], ROH/HCl/ether [168][169][170], and Tf 2 NH [171] to catalyze polymerization of the common lactones, cyclic carbonates, and lactides has been established, the mechanisms of the reactions were proposed but not explored in detail. In [150], the thermochemistry of cationic ring-opening of TMC and 5-methylene-1,3-dioxan-2-one was estimated by quantum-chemical modeling at the HF/3-21G** level of theory, but the results of such modeling do not correspond to the subject of our review.…”

Section: Acid-catalyzed Ropmentioning

confidence: 99%

DFT Modeling of Organocatalytic Ring-Opening Polymerization of Cyclic Esters: A Crucial Role of Proton Exchange and Hydrogen Bonding

Nifant’ev

Ivchenko

2019

Polymers

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Organocatalysis is highly efficient in the ring-opening polymerization (ROP) of cyclic esters. A variety of initiators broaden the areas of organocatalysis in polymerization of different monomers, such as lactones, cyclic carbonates, lactides or gycolides, ethylene phosphates and phosphonates, and others. The mechanisms of organocatalytic ROP are at least as diverse as the mechanisms of coordination ROP; the study of these mechanisms is critical in ensuring the polymer compositions and architectures. The use of density functional theory (DFT) methods for comparative modeling and visualization of organocatalytic ROP pathways, in line with experimental proof of the structures of the reaction intermediates, make it possible to establish these mechanisms. In the present review, which continues and complements our recent manuscript that focused on DFT modeling of coordination ROP, we summarized the results of DFT modeling of organocatalytic ROP of cyclic esters and some related organocatalytic processes, such as polyester transesterification. 4 of 49 were found to be polymerizable due to strain in the ester group. In addition, the predominance of high-energy coiled conformations in linear homopolymers the formed from PDO, εCL and GL was proportionately less than extended conformations, in comparison to the inactive monomer γBL. However, while the prevalence of coiled conformations over extended conformations was expected for poly(LA), this factor does not affected the reactivity of lactides. Very good agreement between the experimental and calculated data for ROP of GL, l-LA and (R,S)-lactide [47] should be separately noted. 4-(Dimethylamino)pyridine (DMAP) and Related CompoundsDMAP was the first employed organocatalyst in polymer synthesis. In 2001, Nederberg et al. [48] reported the "first organocatalytic living polymerization" (Ð M < 1.2) of L-lactide (l-LA) mediated by DMAP or 4-pyrrolidinopyridine in the presence of ROH initiators. Four years later [49], Feng and Dong reported polymerization of ε-caprolactone (εCL) catalyzed by DMAP in the presence of chitozane as an initiator. Bourissou et al. studied the mechanism of DMAP-catalyzed ROP of l-LA and five-membered lactic O-carboxylic anhydride (lacOCA) [50]. Two possible reaction pathways were analyzed at the B3LYP/6-31G(d) level of theory [39,40,51]; the solvent effect of dichloromethane was taken into account through the PCM/SCRF model [52]. The modeled reaction was the methanolysis of l-LA or lacOCA; alternative nucleophilic/monomer (Scheme 1a) and basic/alcohol (Scheme 1b) activation mechanisms were proposed for these reactions, and then analyzed by DFT optimization of the key reaction intermediates and transition states, if necessary. Scheme 1. Schematic representation of the nucleophilic/monomer (a) and basic/alcohol (b) mechanisms for (Dimethylamino)pyridine (DMAP)-catalyzed methanolysis of l-LA. Author Contributions: Conceptualization, P.I.; Methodology, I.N. and P.I.; Writing-Original draft preparation, P.I.; Writing-Review and editing, I.N. and P.I.; V...

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“…In 1971 Dittrich and Schulz [147] were the first to report their unsuccessful polymerization of lactide with cationic compound. Later in 1980s screened a number of acidic compounds, among which trifluoromethane sulfonic acid (triflic acid, HOTf) and methyl triflate (MeOTf) proved to be useful initiators for the cationic ring opening polymerization reaction of various lactones including β-propiolactone (PL), caprolactone (CL), valerolactone (VL), lactide and glycolide [148][149][150][151]. In case of lactide reactions were performed in nitrobenzene for 48 hours and at optimized 50 • C. They also proposed a two step propagation mechanism using end group analysis by 1 H NMR.…”

Section: Cationic Ring-opening Polymerizationmentioning

confidence: 99%

Structure-Processing-Property Relationship of Poly(Glycolic Acid) for Drug Delivery Systems 1: Synthesis and Catalysis

Singh¹,

Tiwari²

2010

International Journal of Polymer Science

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Till date, market is augmented with a huge number of improved drug delivery systems. The success in this area is basically due to biodegradable polymers. Although conventional systems of drug delivery utilizing the natural and semisynthetic polymers so long but synthetic polymer gains success in the controlled drug delivery area due to better degradation profile and controlled network and functionality. The polyesters are the most studied class group due the susceptible ester linkage in their backbone. The Poly(glycolic Acid) (PGA), Poly(lactic acid) (PLA), and Polylactide-co-glycolide (PLGA) are the best profiled polyesters and are most widely used in marketed products. These polymers, however, still are having drawbacks which failed them to be used in platform technologies like matrix systems, microspheres, and nanospheres in some cases. The common problems arose with these polymers are entrapment inefficiency, inability to degrade and release drugs with required profile, and drug instability in the microenvironment of the polymers. These problems are forcing us to develop new polymers with improved physicochemical properties. The present review gave us an insight in the various structural elements of Poly(glycolic acid), polyester, with in depth study. The first part of the review focuses on the result of studies related to synthetic methodologies and catalysts being utilized to synthesize the polyesters. However the author will also focus on the effect of processing methodologies but due some constraints those are not included in the preview of this part of review.

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Polylactones. 10. Cationic polymerization of .delta.-valerolactone by means of alkylating reagents

Cited by 34 publications

References 4 publications

Bismuth‐Triflate‐Catalyzed Polymerizations of ε‐Caprolactone

Bismuth‐Triflate‐Catalyzed Polymerizations of ε‐Caprolactone

DFT Modeling of Organocatalytic Ring-Opening Polymerization of Cyclic Esters: A Crucial Role of Proton Exchange and Hydrogen Bonding

Structure-Processing-Property Relationship of Poly(Glycolic Acid) for Drug Delivery Systems 1: Synthesis and Catalysis

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