Polymerization kinetics of <i>rac</i>‐lactide initiated with alcohol/stannous octoate using <i>in situ</i> attenuated total reflectance‐fourier transform infrared spectroscopy: An initiator study

Moravek, Scott J.; Messman, Jamie M.; Storey, Robson F.

doi:10.1002/pola.23196

Cited by 18 publications

(10 citation statements)

References 10 publications

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“…In view of the fast overall conversions observed for the ROTEP reactions performed by first allowing 2 to react 24 h with BnOH, we used in situ IR monitoring by React-IR to obtain accurate and precise kinetic data. Kinetic measurements of the ring-opening polymerization of LA using Sn(oct) 2 were previously measured with React-IR using single-wavelength analysis. − In preliminary experiments using this method we obtained variable and inconsistent results depending on the IR peak selected. This problem was avoided by using spectral deconvolution and global fitting in the 1900–900 cm –1 region to obtain relative amounts of rac -LA and PLA per spectrum collected.…”

Section: Resultsmentioning

confidence: 99%

Mechanism of the Polymerization of rac-Lactide by Fast Zinc Alkoxide Catalysts

et al. 2017

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The ring-opening transesterification polymerization (ROTEP) of rac-lactide (rac-LA) using LZn catalysts (L = ligand having phenolate, amine, and pyridine donors with variable para substituents X on the bound phenolate donor; X = NO, Br, t-Bu, OMe) was evaluated through kinetics experiments and density functional theory, with the aim of determining how electronic modulation of the ligand framework influences polymerization rate, selectivity, and control. After determination that zinc-ethyl precatalysts required 24 h of reaction with benzyl alcohol to convert to active alkoxide complexes, the subsequently formed species proved to be active and fairly selective, polymerizing up to 300 equiv of rac-LA in 6-10 min while yielding isotactic (P = 0.72-0.78) polylactide (PLA) with low dispersities: Đ = 1.06-1.17. In contrast to previous work with aluminum catalysts for which electronic effects of ligand substituents were significant (Hammett ρ = +1.2-1.4), the LZn systems exhibited much less of an effect (ρ = +0.3). Density functional calculations revealed details of the initiation and propagation steps, enabling insights into the high isotacticity and the insensitivity of the rate on the identity of X.

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Section: Resultsmentioning

confidence: 99%

Mechanism of the Polymerization of rac-Lactide by Fast Zinc Alkoxide Catalysts

et al. 2017

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“…One interesting aspect of the lactide ring‐opening reaction is the flexibility in designing different molecular architectures by employing multifunctional initiators. Different branched structures such as star‐shaped with arm numbers from 3 to 6, dendrimers, comb‐like, and barbell‐like molecules are synthesized by applying this strategy. An alternative procedure for the in situ synthesis of branched PLA is to use co‐monomers bearing initiation groups, such as 2,2‐ bis (hydroxymethyl) butyric acid in the presence of a tertiary amine, glycidol, and 5‐hydroxymethyl‐1,4‐dioxane‐2‐one .…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of polylactides with different branched architectures

Nouri

Dubois

Lafleur

2015

J Polym Sci B Polym Phys

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Star-shaped and comb-like poly(L-Lactide)s (PLA) are produced by employing multifunctional initiators, and hyperbranched structure is prepared using a cyclic co-monomer with hydroxyl group. FTIR, size exclusion chromatography, and H-NMR techniques are employed to characterize the synthesized polymers, validating the formation of desired structures with chain lengths above the critical length for entanglement. After characterization of the synthesized polymers, the effect of branching on PLA properties is investigated by comparing the crystallization and rheological behavior of branched PLAs to those of a linear commercial grade. Differential scanning calorimetry and optical microscopy observations reveal a remark-able improvement in PLA crystallization due to the nucleation role of branching points. Moreover, synthesized polylactides exhibit strain hardening behavior during elongational viscosity measurements by a sentmanat extension rheometer platform. Significant improvements in crystallization and elongational rheology behavior of the synthesized polymers support the achievement of branched polymer structures.

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“…The signicance of the relationships between macromolecule architectures and their properties has recently been recognized. Different polymer structures such as star-shaped with several arm numbers, [32][33][34][35] barbell-shaped, 36,37 comb-shaped, 38,39 and dendrimers 40,41 were synthesized. A lot of reports on the effect of branching, including branch structure and branch degree, showed that branching may accelerate or decelerate the crystallization process and inuence the melting behavior [42][43][44] and the rheological properties.…”

Section: Introductionmentioning

confidence: 99%

Facile synthesis and comparative study of poly(l-lactide) with linear-comb and star-comb architecture

et al. 2015

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In this work, two series of linear-comb and star-comb well defined graft poly(L-lactide) (PLLA) have been synthesized conveniently by one-pot ring-opening polymerization (ROP) of L-lactide using functionalized polybutadiene macroinitiators. The used organocatalyst of 1, 8-diazabicyclo[5,4,0]undec-7-ene (DBU) allows the polymerization of L-lactide proceeds rapidly at room temperature. Kinetic studies of the ROP reaction in this system indicate a first-order kinetic in monomer concentration.1 H NMR and GPC techniques are employed to characterize the synthesized polymers, validating the formation of desired comb structures with controllable chain length. Linear-comb and star-comb graft PLLA were comparatively studied as well as with linear PLLA by DSC and POM. The results reveal that comb structure makes a remarkable improvement of PLLA crystallization ability in both crystallinity and growth rate of spherulites. Furthermore, the more compacted star-comb structure imposes restriction on chain mobility, which weakens the growth effect to some extent. It is found that the glass transition temperature (Tg) and melting temperature (Tm) significantly depend on the side chain length and backbone structure. Rheological studies of both melt and instinct viscosity of the solution show that star-comb PLLA has the lowest hydrodynamic volume compared with linear-comb PLLA and linear PLLA.Polylactide (PLA) derived from renewable resources has drawn significant attention due to its well biodegradable/biocompatible properties and the other concerns associated with the use of petroleum-based products. 1-3 High molecular weight PLA and its copolymers are one of the most widely utilized polymers in the field of biomedical materials 4-8 . Due to the extremely high mechanical strength, it has been used as commodity and industrial materials as well as clinically in medical applications, 9-10 orthopaedic screw, 11-12 scaffolds, 13-15 etc.PLA can be directly prepared from lactic acid by polycondensation under azeotropic distillation conditions referred as poly(lactic acid) [16][17][18] . Ring-opening polymerization (ROP) of lactide is another effective route to synthesize PLA with higher molecular weight and lower polydispersity 19 . Stannous octoate (Sn(Oct)2) is the most common catalyst for ROP of lactide 20 . However, tin based catalysts are less than ideal from both chemical and biological perspective. The organic catalysts now appear as viable substitutes for classical metallic catalysts 21-23 .Non-metallic ROP processes are demanded for sustainable and environmentally friendly products, especially in microelectronic 24 and biomedical 25-26 applications. In 2001, Hedrick et al. first reported N-heterocyclic carbenes as novel metal-free nucleophilic catalysts for the ROP of cyclic ester monomers 27 . Among those catalysts, the commercial available amidine and guanidine (such as 1,5,7-triazabicyclo[4,4,0]dec-5-ene (TBD) and 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU)) provide better control of molecular weight and highly efficient at room...

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Polymerization kinetics of rac‐lactide initiated with alcohol/stannous octoate using in situ attenuated total reflectance‐fourier transform infrared spectroscopy: An initiator study

Cited by 18 publications

References 10 publications

Mechanism of the Polymerization of rac-Lactide by Fast Zinc Alkoxide Catalysts

Mechanism of the Polymerization of rac-Lactide by Fast Zinc Alkoxide Catalysts

Synthesis and characterization of polylactides with different branched architectures

Facile synthesis and comparative study of poly(l-lactide) with linear-comb and star-comb architecture

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