Laurie E. Breyfogle

Bio: Laurie E. Breyfogle is an academic researcher from University of Minnesota. The author has contributed to research in topics: Polymerization & Lactide. The author has an hindex of 6, co-authored 6 publications receiving 1619 citations.

A highly active zinc catalyst for the controlled polymerization of lactide.

Abstract: We report the preparation, structural characterization, and detailed lactide polymerization behavior of a new Zn(II) alkoxide complex, (L1ZnOEt)2 (L1 = 2,4-di-tert-butyl-6-{[(2‘-dimethylaminoethyl)methylamino]methyl}phenolate). While an X-ray crystal structure revealed the complex to be dimeric in the solid state, nuclear magnetic resonance and mass spectrometric analyses showed that the monomeric form L1ZnOEt predominates in solution. The polymerization of lactide using this complex proceeded with good molecular weight control and gave relatively narrow molecular weight distribution polylactide, even at catalyst loadings of <0.1% that yielded Mn as high as 130 kg mol-1. The effect of impurities on the molecular weight of the product polymers was accounted for using a simple model. Detailed kinetic studies of the polymerization reaction enabled integral and nonintegral orders in L1ZnOEt to be distinguished and the empirical rate law to be elucidated, −d[LA]/dt = kp[L1ZnOEt][LA]. These studies also showed ...

Highly active zinc catalyst for the controlled polymerization of lactide.

Abstract: We report the preparation, structural characterization, and detailed lactide polymerization behavior of a new Zn(II) alkoxide complex, (L(1)ZnOEt)(2) (L(1) = 2,4-di-tert-butyl-6-{[(2'-dimethylaminoethyl)methylamino]methyl}phenolate). While an X-ray crystal structure revealed the complex to be dimeric in the solid state, nuclear magnetic resonance and mass spectrometric analyses showed that the monomeric form L(1)ZnOEt predominates in solution. The polymerization of lactide using this complex proceeded with good molecular weight control and gave relatively narrow molecular weight distribution polylactide, even at catalyst loadings of <0.1% that yielded M(n) as high as 130 kg mol(-)(1). The effect of impurities on the molecular weight of the product polymers was accounted for using a simple model. Detailed kinetic studies of the polymerization reaction enabled integral and nonintegral orders in L(1)ZnOEt to be distinguished and the empirical rate law to be elucidated, -d[LA]/dt = k(p)[L(1)ZnOEt][LA]. These studies also showed that L(1)ZnOEt polymerizes lactide at a rate faster than any other Zn-containing system reported previously. This work provides important mechanistic information pertaining to the polymerization of lactide and other cyclic esters by discrete metal alkoxide complexes.

Mechanistic comparison of cyclic ester polymerizations by novel iron(III)-alkoxide complexes: Single vs multiple site catalysis

Abstract: The complexes Fe2(OCHPh2)6 and L2FeOR (R = Et or CHPh2, L = N,N‘-bis(trimethylsilyl)benzamidinate) were structurally characterized, and comparative studies of the behavior of those compounds comprising the same alkoxide (Ph2HCO-) in polymerizations of e-caprolactone (CL) and d,l-lactide (LA) were performed. Both Fe2(OCHPh2)6 and L2FeOCHPh2 are effective polymerization catalysts, as reflected by molecular weight control, polydispersities, and end group analysis, but the diiron complex generally exhibits greater polymerization control, particularly for CL. Kinetic investigations of the polymerization of CL revealed the same first-order dependence on [CL] for both catalysts, but different orders in [catalyst] that signified a distinct contrast in mechanism. Analysis that invoked the presence of a termination-causing impurity at low concentration yielded a first-order dependence on [Fe2(OCHPh2)6], but the order in [L2FeOCHPh2] was found to be one-half. This fractional dependence was interpreted by using a mod...

Comparison of structurally analogous Zn2, Co2, and Mg2 catalysts for the polymerization of cyclic esters

Abstract: Three dimetallic monoethoxide complexes supported by a binucleating phenoxide ligand, LM2Cl2OEt (M = Zn, Co, or Mg), were prepared and shown by X-ray crystallography to be structurally analogous. Comparative studies of their cyclic ester polymerization reactivity revealed different trends for reactions with e-caprolactone and lactide, however, implicating complicated effects of metal ion variation in these polymerizations.

Chemical Routes for the Transformation of Biomass into Chemicals

Abstract: 3.2.3. Hydroformylation 2467 3.2.4. Dimerization 2468 3.2.5. Oxidative Cleavage and Ozonolysis 2469 3.2.6. Metathesis 2470 4. Terpenes 2472 4.1. Pinene 2472 4.1.1. Isomerization: R-Pinene 2472 4.1.2. Epoxidation of R-Pinene 2475 4.1.3. Isomerization of R-Pinene Oxide 2477 4.1.4. Hydration of R-Pinene: R-Terpineol 2478 4.1.5. Dehydroisomerization 2479 4.2. Limonene 2480 4.2.1. Isomerization 2480 4.2.2. Epoxidation: Limonene Oxide 2480 4.2.3. Isomerization of Limonene Oxide 2481 4.2.4. Dehydroisomerization of Limonene and Terpenes To Produce Cymene 2481

Controlled ring-opening polymerization of lactide and glycolide.

Abstract: 23 Stereocontrol of Lactide ROP 6164 231 Isotactic Polylactides 6164 232 Syndiotactic Polylactides 6166 233 Heterotactic Polylactides 6166 3 Anionic Polymerization 6166 4 Nucleophilic Polymerization 6168 41 Mechanistic Considerations 6168 42 Catalysts 6169 421 Enzymes 6169 422 Organocatalysts 6169 43 Stereocontrol of Lactide ROP 6170 44 Depolymerization 6170 5 Cationic Polymerization 6170 6 Conclusion and Perspectives 6171 7 Acknowledgments 6173 8 References and Notes 6173

Synthesis of polycaprolactone: a review

Abstract: Polycaprolactone (PCL) is an important polymer due to its mechanical properties, miscibility with a large range of other polymers and biodegradability. Two main pathways to produce polycaprolactone have been described in the literature: the polycondensation of a hydroxycarboxylic acid: 6-hydroxyhexanoic acid, and the ring-opening polymerisation (ROP) of a lactone: e-caprolactone (e-CL). This critical review summarises the different conditions which have been described to synthesise PCL, and gives a broad overview of the different catalytic systems that were used (enzymatic, organic and metal catalyst systems). A surprising variety of catalytic systems have been studied, touching on virtually every section of the periodic table. A detailed list of reaction conditions and catalysts/initiators is given and reaction mechanisms are presented where known. Emphasis is put on the ROP pathway due to its prevalence in the literature and the superior polymer that is obtained. In addition, ineffective systems that have been tried to catalyse the production of PCL are included in the electronic supplementary information for completeness (141 references).

Organocatalytic ring-opening polymerization.

Abstract: Modern synthetic methods have revolutionized polymer chemistry through the development of new and powerful strategies for the controlled synthesis of complex polymer architectures. 1-5 Many of these developments were spawned by new classes of transition metal catalysts for the synthesis of new polyolefin microstructures, 5 the design of highly efficient families of “living” polymerization strategies for the synthesis of block, graft, and star polymers, 6-12 controlled methods for the synthesis of dendritic macromolecules, 3,13,14