Journal ArticleDOI
Guanidine and Amidine Organocatalysts for Ring-Opening Polymerization of Cyclic Esters
Bas G. G. Lohmeijer,Russell C. Pratt,Frank A. Leibfarth,John W. Logan,David A. Long,Andrew P. Dove,Fredrik Nederberg,Jeongsoo Choi,Charles G. Wade,Robert M. Waymouth,James L. Hedrick +10 more
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TLDR
In this article, the ring-opening polymerization (ROP) of cyclic esters such as lactide (LA), δ-valerolactone (VL), and e-caprolactone(CL) was achieved.Abstract:
1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD), N-methyl-TBD (MTBD), and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) are effective organocatalysts for the ring-opening polymerization (ROP) of cyclic esters such as lactide (LA), δ-valerolactone (VL), and e-caprolactone (CL). TBD is shown to polymerize LA, VL, and CL in a fast and controlled manner, whereas MTBD and DBU polymerized LA and addition of a thiourea cocatalyst led to the ROP of VL and CL being achieved. Each of the catalysts produced polymers displaying high end group fidelity, good correlation between theoretical and observed molecular weight, and linear relationships between conversion and molecular weight. The enhanced activity of TBD relative to MTBD and DBU is attributed to its bifunctionality, enabling the simultaneous activation of both the cyclic ester monomer and the alcohol group of the initiator/propagating species. Temperature-dependent NMR studies generated individual association constants for MTBD with benzyl alcohol and thiourea with VL. ...read more
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Tough polylactide graft copolymers
Journal ArticleDOI
Synergetic Organocatalysis for Eliminating Epimerization in Ring-Opening Polymerizations Enables Synthesis of Stereoregular Isotactic Polyester.
Maosheng Li,Yue Tao,Yue Tao,Jiadong Tang,Jiadong Tang,Yanchao Wang,Yanchao Wang,Xiaoyong Zhang,Youhua Tao,Xianhong Wang +9 more
TL;DR: An effective bifunctional single-molecule organocatalysis for selective ring-opening polymerization of OCAs without epimerization is described, allowing sustainable and scalable synthesis of a stereoregular functional polyester.
Journal ArticleDOI
Organic Ring-Opening Polymerization Catalysts: Reactivity Control by Balancing Acidity
Binhong Lin,Robert M. Waymouth +1 more
TL;DR: In this article, an array of ureas or thioureas and organic bases were evaluated to assess the effect of the acidity of the urea (thiourea) and the basicity of base cocatalyst on the activity for ring-opening polymerization.
Journal ArticleDOI
Effects of block copolymer properties on nanocarrier protection from in vivo clearance
Suzanne M. D'Addio,Walid Saad,Steven M. Ansell,John J. Squiers,Douglas H. Adamson,Margarita Herrera-Alonso,Adam R. Wohl,Thomas R. Hoye,Christopher W. Macosko,Lawrence D. Mayer,Christine Vauthier,Robert K. Prud'homme +11 more
TL;DR: In this paper, the authors proposed guidelines for optimizing block copolymer structure to maximize circulation of nanocarriers formed by rapid precipitation and directed assembly, relating to the relative sizes of hydrophilic and hydrophobic blocks, the hydrophobicity of the anchoring block, the absolute size of the PEG block, and polymer crystallinity.
Journal ArticleDOI
Formation of Well-Defined, Functional Nanotubes via Osmotically Induced Shape Transformation of Biodegradable Polymersomes.
Loai K. E. A. Abdelmohsen,David S. Williams,Jan Pille,Sema G. Ozel,Roger S. M. Rikken,Daniela A. Wilson,Jan C. M. van Hest +6 more
TL;DR: The spontaneous elongation of spherical polymersomes comprising the biodegradable copolymer poly(ethylene glycol)-b-poly(d,l-lactide) into well-defined nanotubes is demonstrated, establishing a novel platform for the creation of biocompatible, high-aspect ratio nanoparticles for biomedical research.
References
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Journal ArticleDOI
Controlled ring-opening polymerization of lactide and glycolide.
TL;DR: This work focuses on the characterization of the phytochemical components of Lactide ROP and their role in the regulation of cell reprograming.
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Polymerization of Lactide with Zinc and Magnesium β-Diiminate Complexes: Stereocontrol and Mechanism
Bradley M. Chamberlain,Ming Cheng,David Roger Moore,Tina M. Ovitt,Emil B. Lobkovsky,Geoffrey W. Coates +5 more
TL;DR: The substituents on the beta-diiminate ligand exert a significant influence upon the course of the polymerizations, affecting both the degree of stereoselectivity and the rate of polymerization.
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A review of biodegradable polymers: uses, current developments in the synthesis and characterization of biodegradable polyesters, blends of biodegradable polymers and recent advances in biodegradation studies
TL;DR: A review of the uses of biodegradable polymers in terms of their relevance within current plastic waste management of packaging materials, biomedical applications and other uses is presented in this paper.
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Extension of the self-consistent spectrophotometric basicity scale in acetonitrile to a full span of 28 pKa units: unification of different basicity scales.
Ivari Kaljurand,Agnes Kütt,Lilli Sooväli,Toomas Rodima,Vahur Mäemets,and Ivo Leito,Ilmar A. Koppel +6 more
TL;DR: The earlier compiled self-consistent spectrophotometric basicity scale in acetonitrile (AN) was expanded to range from 3.8 to 32.0 pK(a) units, that is 28 orders of magnitude, and 54 new relative basicity measurements were carried out and 37 new compounds were introduced to the scale.
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Stereochemistry of Lactide Polymerization with Chiral Catalysts: New Opportunities for Stereocontrol Using Polymer Exchange Mechanisms
Tina M. Ovitt,Geoffrey W. Coates +1 more
TL;DR: A polymer exchange mechanism is proposed to account for the PLA microstructures resulting from rac-4, which polymerizes meso-lactide to syndiotactic poly(lactic acid) (PLA) and heterotactic and isotactic stereoblock PLA, respectively.