skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: Preparation of multiblock copolymers via step-wise addition of l -lactide and trimethylene carbonate
Poly( l -lactide) (PLA) is a bioderived and biodegradable polymer that has limited applications due to its hard and brittle nature. Incorporation of 1,3-trimethylene carbonate into PLA, in a block copolymer fashion, improves the mechanical properties, while retaining the biodegradability of the polymer, and broadens its range of applications. However, the preparation of 1,3-trimethylene carbonate (TMC)/ l -lactide (LA) copolymers beyond diblock and triblock structures has not been reported, with explanations focusing mostly on thermodynamic reasons that impede the copolymerization of TMC after lactide. We discuss the preparation of multiblock copolymers via the ring opening polymerization (ROP) of LA and TMC, in a step-wise addition, by a ferrocene-chelating heteroscorpionate zinc complex, {[fc(PPh 2 )(BH[(3,5-Me) 2 pz] 2 )]Zn(μ-OCH 2 Ph)} 2 ([(fc P,B )Zn(μ-OCH 2 Ph)] 2 , fc = 1,1′-ferrocenediyl, pz = pyrazole). The synthesis of up to pentablock copolymers, from various combinations of LA and TMC, was accomplished and the physical, thermal, and mechanical properties of the resulting copolymers evaluated.  more » « less
Award ID(s):
1638163
PAR ID:
10062521
Author(s) / Creator(s):
; ; ; ; ;
Date Published:
Journal Name:
Chemical Science
Volume:
9
Issue:
8
ISSN:
2041-6520
Page Range / eLocation ID:
2168 to 2178
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; (, Journal of the American Chemical Society)
    Poly(lactic acid) (PLA) offers a renewable and degradable alternative to petroleum-based plastic, but its mechanical properties are not ideal for many applications. Herein, we describe the synthesis and polymerization of oxo-3,8-dioxabicyclo[3.2.1]octane (ODO), a bio-derived bicyclic lactone, and show that copolymers of L-lactide (LA) with small amounts of ODO have improved mechanical properties over PLA. Homopolymerization of ODO to poly(oxo-3,8-dioxabicyclo[3.2.1]octane) (PODO) is optimized for both solution-phase, organocatalytic and melt-phase, metal-catalyzed conditions. In comparison to the monocyclic analog, ε-caprolactone (CL), ODO has a lower enthalpy of polymerization and faster rate of polymerization. PODO is an amorphous, elastomeric polyester that has a 90 °C higher Tg than poly(ε-caprolactone) (PCL). Statistical copolymerization of LA with small fractions of ODO yields tough and transparent thermoplastics that have over 12× elongation at break compared to native PLA, while maintaining Tg, Young’s modulus (E), and yield strength. Together, these results describe how the incorporation of the tetrahydrofuran ring alters polymerizability and the thermomechanical properties of the homopolymer and copolymer materials. 
    more » « less
  2. ; ; (, Faraday Discussions)
    Polylactide (PLA) is a commercial and sustainably sourced aliphatic polyester but its applications have been limited by its low toughness. The insertion of a rubbery segment within the PLA backbone is among the promising strategies to enhance the mechanical properties of PLA while retaining sustainability. Herein, we disclose a catalytic stereoretentive ring-opening metathesis polymerization process to access high molar mass (Mnexp up to 127.9 kg/mol) all-cis telechelic polycyclooctene (PCOE) at low catalyst loadings. The use of cis-1,4-diacetoxy-2-butene as a chain-transfer agent in the presence of stereoretentive dithiolate Ru carbenes afforded precise control over the cis content, the molar mass, and the introduction of acetoxy chain ends. Subsequent hydrolysis of the acetoxy motifs followed by chain extension via ring-opening polymerization of D,L-lactide yielded high molar mass (Mnexp up to 105.0 kg/mol) all-cis PLA ABA triblock copolymers. The influence of the molar mass of the all-cis PCOE over the thermal and mechanical properties of the ABA triblock was investigated. 
    more » « less
  3. ; ; ; ; ; ; ; (, Journal of Applied Polymer Science)
    ABSTRACT This study investigates the morphological, thermal, mechanical, and bioactive properties of centrifugally spun fibrous composites made from poly(D,L‐lactide)/poly(3‐hydroxybutyrate) (PLA/PHB) blends with zinc oxide (ZnO) and hydroxyapatite (Hap) nanoparticles. A 75/25 PLA/PHB weight ratio was chosen to balance mechanical and thermal properties. The precursor solution viscosities ranged from 0.25 to 0.50 Pa s, increasing with nanoparticle incorporation probably due to polymer‐nanoparticle interactions. SEM revealed a uniform fibrous morphology, with diameters of 1.21 for PLA/PHB, 2.65 for PLA/ZnO/Hap, and 1.80 μm for PLA/PHB/ZnO/Hap. TGA showed two‐step degradation for PLA/PHB fibers, while PLA/PHB/ZnO/Hap degraded in a single step at 249°C, leaving a residue of 9.95%. DSC indicated partial miscibility, with cold crystallization at 85°C (enthalpy: 7.72 J/g), slightly modified by nanoparticle addition. PLA/PHB fibers achieved a Young's modulus of 24.96 ± 3.91 MPa, three times that of pure PLA, but adding ZnO and Hap reduced modulus and tensile strength to 6.03 and 0.29 MPa, retaining suitability for biomedical applications. PLA/PHB/ZnO/Hap fibers exhibited 90%Escherichia coligrowth inhibition and enhanced MC3T3‐E1 cell viability by 120% on day 7. These results highlight their potential for antimicrobial, biocompatible medical devices. 
    more » « less
  4. ; ; ; ; ; ; ; (, Angewandte Chemie International Edition)
    Abstract In an effort to synthesize chemically recyclable thermoplastic elastomers, a redox‐switchable catalytic system was developed to synthesize triblock copolymers containing stiff poly(lactic acid) (PLA) end blocks and a flexible poly(tetrahydrofuran‐co‐cyclohexene oxide) (poly(THF‐co‐CHO) copolymer as the mid‐block. The orthogonal reactivity induced by changing the oxidation state of the iron‐based catalyst enabled the synthesis of the triblock copolymers in a single reaction flask from a mixture of monomers. The triblock copolymers demonstrated improved flexibility compared to poly(l‐lactic acid) (PLLA) and thermomechanical properties that resemble thermoplastic elastomers, including a rubbery plateau in the range of −60 to 40 °C. The triblock copolymers containing a higher percentage of THF versus CHO were more flexible, and a blend of triblock copolymers containing PLLA and poly(d‐lactic acid) (PDLA) end‐blocks resulted in a stereocomplex that further increased polymer flexibility. Besides the low cost of lactide and THF, the sustainability of this new class of triblock copolymers was also supported by their depolymerization, which was achieved by exposing the copolymers sequentially to FeCl3and ZnCl2/PEG under reactive distillation conditions. 
    more » « less
  5. ; ; ; ; ; ; ; ; ; ; et al (, New Journal of Chemistry)
    Reactions of the bicompartmental bis(phenolato) compound 6,6′-methylenebis(2-((bis(pyridin-2-ylmethyl)amino)methyl)-4-chlorophenol)hemihydrate (H 2 L ½H 2 O) with 3d metal( ii ) ions afforded novel fully structurally characterized bridged acetato dinuclear complexes [Mn 2 (HL)(μ 1,2 -OAc) 2 ]PF 6 (1) [Zn 2 (HL)(μ 1,2 -OAc)(H 2 O) 0.75 (MeOH) 0.25 ](PF 6 ) 2 ·0.45(H 2 O) (5) and [Cd 2 (HL)(μ 1,1,2 -OAc)(OAc)(H 2 O)]PF 6 ·H 2 O (6) as well as the polymeric bridged-azido tetranuclear catena -[Cu 4 (HL) 2 (μ 1,1 -N 3 ) 2 (μ 1,3 -N 3 ) 2 ](NO 3 ) 2 ·5H 2 O (4). The complex [Cu 4 (HL) 2 (ClO 4 ) 3 (H 2 O) 5 ](ClO 4 ) 3 ·5H 2 O (2) was partially characterized. In addition, three more dinuclear complexes [Cu 2 (H 2 L)(NO 3 ) 2 (H 2 O) 2 ](NO 3 ) 2 (3), [Cu 2 (HL)(OAc)(CH 3 OH)](PF 6 ) 2 (7) and [Cu 2 (HL)(NCS) 2 ]NO 3 ·2H 2 O (8) were also isolated. All complexes were characterized by CHN elemental analysis, IR and UV-Vis spectroscopy, ESI-MS, conductivity measurements and X-ray single crystal crystallography for compounds 1, 4, 5 and 6, where the bis(phenolato) ligand displayed different deprotonation (H 2 L, HL − and L 2− ). The magnetic susceptibility measurements over the temperature range 2–300 K revealed very weak antiferromagnetic coupling in dimanganese( ii ) 1 ( J = −1.64(1) cm −1 ) and almost negligible magnetic interaction in dicopper( ii ) 2 ( J = 0(3) cm −1 ). In the azido catena -[Cu 4 (HL) 2 (μ 1,1 -N 3 ) 2 (μ 1,3 -N 3 ) 2 ](NO 3 ) 2 ·5H 2 O (4) complex, the J value of −133(3) cm −1 was obtained upon moderate-to-strong antiferromagnetic coupling through the di-μ 1,3 -N 3 -bridged dicopper( ii ) unit with no magnetic interaction between the two copper( ii ) ions in the di-μ 1,1 -N 3 -bridged unit. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Text Encoded Conversion
  • XML
  • Save / Share this Record
  • Send to Email