Solution and melt viscoelastic properties of controlled microstructure poly(lactide)

A series of controlled microstructure poly(lactide) (PLA) samples were synthesized using a novel chiral dinuclear indium catalyst capable of living polymerization of lactide. PLAs with different ratios of L- to D- monomer ratios of 100:0, 90:10, 75:25, 50:50, and 0:100 were investigated. The relationship between intrinsic viscosity and the absolute molar mass distribution of the samples obtained by light scattering gel permeation chromatography in tetrahydrofuran gives [η] = 0.014 + 0.75 Mw, a scaling law of typical coil dimensions of linear macromolecules in good solvent. The melt rheological study includes determination of zero-shear viscosity and its relationship with the molecular weight, the relaxation spectrum, and its relation with molecular weight characteristics, as well as plateau modulus and other important rheological parameters that are helpful in predicting the linear viscoelasticity of PLA. Emphasis is placed on the uniaxial melt behavior of these polymers. At low temperatures, significant strain hardening is observed, which gradually disappears with an increase in temperature and decrease of Hencky strain rate. The K-BKZ constitutive equation is used to model the experimental data. It is concluded that in spite of their linear structure, PLAs exhibit strain hardening which is not due to strain-induced crystallization, and it is solely due to the dynamics of molecular relaxation.

[1]  Spencer C. Knight,et al.  Mechanistic study of the stereoselective polymerization of D,L-lactide using indium(III) halides. , 2010, Journal of the American Chemical Society.

[2]  B. Patrick,et al.  Synthesis and structural studies of chiral indium(III) complexes supported by tridentate diaminophenol ligands. , 2010, Inorganic chemistry.

[3]  T. Watanabe,et al.  Viscoelasticity and extensional rheology of model Cayley-tree polymers of different generations , 2010 .

[4]  A. Janorkar,et al.  Poly(lactic acid) modifications , 2010 .

[5]  J. Okuda,et al.  Chiral indium alkoxide complexes as initiators for the stereoselective ring-opening polymerization of rac-lactide. , 2010, Inorganic chemistry.

[6]  Christophe M. Thomas.  Stereocontrolled ring-opening polymerization of cyclic esters: synthesis of new polyester microstructures. , 2010, Chemical Society reviews.

[7]  J. Okuda,et al.  Indium complexes supported by 1,omega-dithiaalkanediyl-bridged bis(phenolato) ligands: synthesis, structure, and controlled ring-opening polymerization of L-lactide. , 2009, Inorganic chemistry.

[8]  B. Patrick,et al.  Unusually Stable Chiral Ethyl Zinc Complexes: Reactivity and Polymerization of Lactide , 2009 .

[9]  B. Patrick,et al.  A highly active chiral indium catalyst for living lactide polymerization. , 2008, Angewandte Chemie.

[10]  Charlotte K. Williams,et al.  Biocompatible Initiators for Lactide Polymerization , 2008 .

[11]  Richard Stewart,et al.  Going Green: Eco-Friendly Materials and Recycling on Growth Paths , 2008 .

[12]  A. Albertsson,et al.  Branched poly(lactide) synthesized by enzymatic polymerization: effects of molecular branches and stereochemistry on enzymatic degradation and alkaline hydrolysis. , 2007, Biomacromolecules.

[13]  S. Hatzikiriakos,et al.  Synthesis, Characterization, and Viscoelastic Properties of High Molecular Weight Hyperbranched Polyglycerols , 2006 .

[14]  S. Hatzikiriakos,et al.  Rheology and Processing of Molten Poly(methyl methacrylate) Resins , 2006 .

[15]  Jincai Wu,et al.  Recent developments in main group metal complexes catalyzed/initiated polymerization of lactides and related cyclic esters , 2006 .

[16]  H. Münstedt,et al.  Molecular Characterization of Semi-Fluorinated Copolymers with a Controlled Amount of Long-Chain Branching , 2006 .

[17]  J. Dorgan,et al.  Fundamental solution and single‐chain properties of polylactides , 2005 .

[18]  J. Dorgan,et al.  Melt rheology of variable L-content poly(lactic acid) , 2005 .

[19]  G. McKinley,et al.  Measuring the transient extensional rheology of polyethylene melts using the SER universal testing platform , 2005 .

[20]  Odile Dechy-Cabaret,et al.  Controlled ring-opening polymerization of lactide and glycolide. , 2004, Chemical reviews.

[21]  H. Yamane,et al.  Poly(D-lactic acid) as a rheological modifier of poly(L-lactic acid): Shear and biaxial extensional flow behavior , 2004 .

[22]  David J. Williams,et al.  Remarkable stereocontrol in the polymerization of racemic lactide using aluminum initiators supported by tetradentate aminophenoxide ligands. , 2004, Journal of the American Chemical Society.

[23]  A. Duda,et al.  Stereocontrolled polymerization of racemic lactide with chiral initiator: combining stereoelection and chiral ligand-exchange mechanism. , 2004, Journal of the American Chemical Society.

[24]  Ashwini K. Agrawal,et al.  Advances in the Production of Poly(Lactic Acid) Fibers. A Review , 2003 .

[25]  C. Friedrich,et al.  Van Gurp-Palmen-plot: a way to characterize polydispersity of linear polymers , 2001 .

[26]  L. Palade,et al.  Melt Rheology of High l-Content Poly(lactic acid) , 2001 .

[27]  H. Winter,et al.  Relaxation time spectra of star polymers , 2000 .

[28]  Joshua S. Williams,et al.  Melt rheology of poly(lactic acid): Entanglement and chain architecture effects , 1999 .

[29]  M. Mackay,et al.  Rheological properties of poly(lactides). Effect of molecular weight and temperature on the viscoelasticity of poly(l‐lactic acid) , 1999 .

[30]  W. Burchard.  Solution Properties of Branched Macromolecules , 1999 .

[31]  C. Macosko,et al.  Nonlinear shear and extensional rheology of long-chain randomly branched polybutadiene , 1998 .

[32]  Š. Podzimek.  The use of GPC coupled with a multiangle laser light scattering photometer for the characterization of polymers. On the determination of molecular weight, size and branching , 1994 .

[33]  H. Winter,et al.  Molecular weight dependence of relaxation time spectra for the entanglement and flow behavior of monodisperse linear flexible polymers , 1994 .

[34]  H. Winter,et al.  The relaxation of polymers with linear flexible chains of uniform length , 1990 .

[35]  Kurt F. Wissbrun,et al.  Melt Rheology and Its Role in Plastics Processing: Theory and Applications , 1990 .

[36]  H. Henning Winter,et al.  Determination of discrete relaxation and retardation time spectra from dynamic mechanical data , 1989 .

[37]  S. Edwards,et al.  The Theory of Polymer Dynamics , 1986 .

[38]  C. Macosko,et al.  An Integral Constitutive Equation for Mixed Flows: Viscoelastic Characterization , 1983 .

[39]  H. Fujita,et al.  Flory's Viscosity Factor for the System Polystyrene + Cyclohexane at 34.5 °C , 1980 .