A literature review is presented regarding the synthesis, and physicochemical, chemical, and mechanical properties of poly(lactic acid)(PLA). Poly(lactic acid) exists as a polymeric helix, with an orthorhombic unit cell. The tensile properties of PLA can vary widely, depending on whether or not it is annealed or oriented or what its degree of crystallinity is. Also discussed are the effects of processing on PLA. Crystallization and crystallization kinetics of PLA are also investigated. Solution and melt rheology of PLA is also discussed. Four different power-law equations and 14 different Mark–Houwink equations are presented for PLA. Nuclear magnetic resonance, UV–VIS, and FTIR spectroscopy of PLA are briefly discussed. Finally, research conducted on starch–PLA composites is introduced.

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A Literature Review of Poly(Lactic Acid)

Solubility Parameters - An Introduction C.M. Hansen Hildebrand Parameters and Basic Polymer Solution Thermodynamics Hansen Solubility Parameters Methods and Problems in the Determination of Partial Solubility Parameters Calculation of the Dispersion Solubility Parameter deltad Calculation of the Polar Solubility Parameter deltap Calculation of the Hydrogen Bonding Solubility Parameter deltah Supplementary Calculations And Procedures Hansen Solubility Parameters for Water Theory - The Prigogine Corresponding States Theory, the c12 Interaction Parameter, and the Hansen Solubility Parameters C.M. Hansen Hansen Solubility Parameters (HSP) Resemblance Between Predictions of Hansen Solubility Parameters and Corresponding States Theories The c12Parameter and Hansen Solubility Parameters Comparison of Calculated and Experimental c12 Parameters General Discussion Postscript Statistical Thermodynamic Calculations of the Hydrogen Bonding, Dipolar, and Dispersion Solubility Parameters C. Panayiotou Theory Applications Discussion and Conclusions Appendix I: The Acid Dimerization Appendix II: An Alternative Form of the Polar Term Appendix III: A Group-Contribution Method for the Prediction of delta and deltaD Hansen Solubility Parameters (HSP) in Thermodynamic Models for Polymer Solutions G.M. Kontogeorgis Group Contribution Methods for Estimating Properties of Polymers Activity Coefficients Models Using the HSP Conclusions and Future Challenges Appendix I: An Expression of the FH Model for Multicomponent Mixture Methods of Characterization - Polymers C.M. Hansen Calculation of Polymer HSP Solubility - Examples Swelling - Examples Melting Point Determinations - Effect of Temperature Environmental Stress Cracking Intrinsic Viscosity Measurements Other Measurement Techniques Methods of Characterization - Surfaces C.M. Hansen Hansen Solubility Parameter Correlations with Surface Tension (Surface Free Energy) Method to Evaluate the Cohesion Energy Parameters for Surfaces A Critical View of the Critical Surface Tensions A Critical View of the Wetting Tension Additional Hansen Solubility Parameter Surface Characterizations and Comparisons Self-Stratifying Coatings Maximizing Physical Adhesion Methods of Characterization for Pigments, Fillers, and Fibers C.M. Hansen Methods to Characterize Pigment, Filler, and Fiber Surfaces Discussion - Pigments, Fillers, and Fibers Hansen Solubility Parameter Correlation of Zeta Potential for Blanc Fixe Carbon Fiber Surface Characterization Controlled Adsorption (Self-Assembly) Applications - Coatings and Other Filled Polymer Systems C.M. Hansen Solvents Techniques for Data Treatment Solvents and Surface Phenomena in Coatings (Self-Assembly) Polymer Compatibility Hansen Solubility Parameter Principles Applied to Understanding Other Filled Polymer Systems Hansen Solubility Parameters of Asphalt, Bitumen and Crude Oils P. Redelius Models of Bitumen Asphaltenes Molecular Weight Polarity Solubility Parameters of Bitumen Testing of Bitumen Solubility Hildebrand Solubility Parameters Hansen Solubility Parameters (HSP) The Solubility Sphere Computer Program for Calculation and Plotting of the Hansen 3D Pseudosphere Components of Bitumen Bitumen and Polymers Crude Oil Turbidimetric Titrations BISOM Test Determination of Hansen Solubility Parameter Values for Carbon Dioxide L.L. Williams Methodology One-Component Hildebrand Parameter as a Function of Temperature and Pressure Three-Component (Hansen) Solubility Parameters - Pure CO2 Temperature and Pressure Effects on HSPs: deltad Temperature and Pressure Effects on HSPs: deltap Temperature and Pressure Effects on HSPs: deltah Addendum Appendix I: Ideal Solubility of Gases in Liquids and Published CO2 Solubility Data Use of Hansen Solubility Parameters to Identify Cleaning Applications for "Designer" Solvents J. Durkee A Variety of Solvents Pathology of Soils HSP of Multiple-Component Soils Method for Calculating HSP of Composites (Soils or Solvents) More Realistic View About Evaluating HSP of Composite Soils Method for Choice of Suitable Solvents Reference Soils for Comparison Identification of Designer Solvents An Open Question - Answered Limiting RA Value For Expected Good Cleaning Performance Application of HSP Methodology to Cleaning Operations Analysis of Capability of Designer Solvents Applications - Chemical Resistance C.M. Hansen Chemical Resistance - Acceptable-or-Not Data Effects of Solvent Molecular Size Chemical Resistance - Examples Special Effects with Water Applications - Barrier Polymers C.M. Hansen Concentration-Dependent Diffusion Solubility Parameter Correlations Based on Permeation Phenomena Solubility Parameter Correlation of Polymer Swelling Solubility Parameter Correlation of Permeation Coefficients for Gases General Considerations Applications - Environmental Stress Cracking in Polymers C.M. Hansen ESC Interpreted Using HSP ESC With Nonabsorbing Stress Cracking Initiators Hansen Solubility Parameters - Biological Materials C.M. Hansen and T. Svenstrup Poulsen Hydrophobic Bonding and Hydrophilic Bonding (Self-Association) DNA Cholesterol Lard Human Skin Proteins - Blood Serum and Zein Chlorophyll and Lignin Wood Chemicals and Polymers Urea Water Surface Mobility Chiral Rotation, Hydrogen Bonding, and Nanoengineering Absorption and Diffusion in Polymers C.M. Hansen Steady State Permeation The Diffusion Equation Surface Resistance Side Effects Film Formation by Solvent Evaporation Anomalous Diffusion (Case II, Super Case II) Applications - Safety and Environment C.M. Hansen Substitution Alternative Systems Solvent Formulation And Personal Protection For Least Risk The Danish Mal System - The Fan Selection of Chemical Protective Clothing Uptake of Contents by a Plastic Container Skin Penetration Transport Phenomena The Future Hansen Solubility Parameter Data and Data Quality Group Contribution Methods Polymers as Points - Solvents as Spheres Characterizing Surfaces Materials and Processes Suggested for Further Attention Theoretical Problems Awaiting Future Resolution Appendices Hansen Solubility Parameters for Selected Solvents with the major contribution of Hanno Priebe Hansen Solubility Parameters for Selected Correlations Solubility Data for the Original 33 Polymers and 88 Solvents Index * Each Chapter contains an Abstract, an Introduction, and a Conclusion. Many chapters may also include Acknowledgements, Additional Discussions or General Comments/Considerations, and chapter-specific Key Words, Abbreviations, and Symbols

Hansen Solubility Parameters: A User's Handbook

Drugs with low water solubility are predisposed to low and variable oral bioavailability and, therefore, to variability in clinical response. Despite significant efforts to "design in" acceptable developability properties (including aqueous solubility) during lead optimization, approximately 40% of currently marketed compounds and most current drug development candidates remain poorly water-soluble. The fact that so many drug candidates of this type are advanced into development and clinical assessment is testament to an increasingly sophisticated understanding of the approaches that can be taken to promote apparent solubility in the gastrointestinal tract and to support drug exposure after oral administration. Here we provide a detailed commentary on the major challenges to the progression of a poorly water-soluble lead or development candidate and review the approaches and strategies that can be taken to facilitate compound progression. In particular, we address the fundamental principles that underpin the use of strategies, including pH adjustment and salt-form selection, polymorphs, cocrystals, cosolvents, surfactants, cyclodextrins, particle size reduction, amorphous solid dispersions, and lipid-based formulations. In each case, the theoretical basis for utility is described along with a detailed review of recent advances in the field. The article provides an integrated and contemporary discussion of current approaches to solubility and dissolution enhancement but has been deliberately structured as a series of stand-alone sections to allow also directed access to a specific technology (e.g., solid dispersions, lipid-based formulations, or salt forms) where required.

Strategies to Address Low Drug Solubility in Discovery and Development

Physical aging of polymers

A review of polymer dissolution

Development of an indirect method of estimating the solubility parameter of high molecular weight polymers. The proposed method of estimating the solubility parameter, like Small's method, is based on group additive constants, but is believed to be superior to Small's method for two reasons: (1) the contribution of a much larger number of functional groups have been evaluated, and (2) the method requires only a knowledge of structural formula of the compound.

A method for estimating both the solubility parameters and molar volumes of liquids

A method for estimating both the solubility parameters and molar volumes of liquids.† Supplement

The glass transition temperature Tg and density of a TGDDM-DDS epoxy resin system were studied as a function of cure times at various cure temperatures. Both Tg and density asymptotically increased toward a maximum value with increasing cure time. The Tg and density measurements were related to the extent of cure, and the relationship in both cases was found to be independent of cure temperature.

Influence of cure conditions on glass transition temperature and density of an epoxy resin

A study was made on the stress relaxation behavior at 25 C of poly(methyl methacrylate) in uniaxial tension as a function of physical aging at both room temperature and 60 C. Test specimens were compression molded at 165 C, then quenched to room temperature and allowed to age for up to 30 days prior to testing. Stress relaxation curves measured after different aging times could be superposed to a single master curve for each aging temperature. Superposition was achieved by applying vertical and horizontal shifts. Hence, the shape of the response curves was not changed by aging. This is in accordance with observations made by Struik for tensile creep curves. Volume changes as a function of physical aging were also determined. Simple exponential relationships were observed between volume and both horizontal and vertical shifts. The horizontal shift implies a shift in the effective time scale caused by a change in free volume. The vertical shifts could be correlated with changes in Young's modulus caused by a change in density. For the range of aging studied, the response time scale varied over nearly two decades of log-time. For the same conditions modulus varied by 30 percent.

Effect of physical aging on stress relaxation of poly(methyl methacrylate)

In order to gain better understanding of the molecular deformation processes occurring in poly-(methyl methacrylate), a series of studies was carried out in uniaxial tension on the simultaneous stress and birefringence response in both constant-strain-rate and stress relaxation experiments. The former covered the temperature range −120 to 75°C and the latter 0 to 90°C. Three deformation mechanisms, i.e., (i) change in intermolecular distance, (ii) distortion of the conformation of the COOCH3 group from its thermal equilibrium state, and (iii) orientation of main-chain segments, are invoked to interpret the experimental results. It is concluded that, in the temperature range from −120 to 75°C and possibly at higher temperatures as well, the polymer chains deform in the small-strain region by an orientation of those chain segments having lower potential-energy barriers to conformational changes and straining those chain segments having higher potential-energy barriers. Subsequent chain orientation of the already strained segments occur in the higher strain regions. Changes in intermolecular distances occur over the entire temperature range from −120 to 90°C, but their magnitude decreases gradually as the temperature increases from −40 to 40°C and then decreases sharply for temperatures above 40°C. Strain-induced distortion of the conformation of the COOCH3 group may involve only rotation of the OCH3 group around the CO bond rather than rotation of the entire ester group itself.

Study of molecular deformation mechanisms in the glassy state. I. Temperature effect on stress-birefringence and strain-birefringence responses of poly(methyl methacrylate)

R. F. Fedors

Papers

A method for estimating both the solubility parameters and molar volumes of liquids

A method for estimating both the solubility parameters and molar volumes of liquids.† Supplement

Influence of cure conditions on glass transition temperature and density of an epoxy resin

Effect of physical aging on stress relaxation of poly(methyl methacrylate)

Study of molecular deformation mechanisms in the glassy state. I. Temperature effect on stress-birefringence and strain-birefringence responses of poly(methyl methacrylate)