BLENDS OF HIGH MOLECULAR WEIGHT POLY(LACTIC ACID) (PLA) WITH COPOLYMERS OF 2-BROMO-3-HYDROXYPROPIONIC ACID AND LACTIC ACID (PLB) A Thesis Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment of the Requirements for the Degree Master of Science Xia Lei May, 2013 BLENDS OF HIGH MOLECULAR WEIGHT POLY(LACTIC ACID) (PLA) WITH COPOLYMERS OF 2-BROMO-3-HYDROXYPROPIONIC ACID AND LACTIC ACID (PLB) Xia Lei Thesis Approved: Accepted: _______________________________ _______________________________ Advisor Dean of the College Dr. Coleen Pugh Dr. Stephen Cheng _______________________________ _______________________________ Faculty Reader Dean of the Graduate School Dr. Li Jia Dr. George Newkome _______________________________ _______________________________ Department Chair Date Dr. Coleen Pugh ii ABSTRACT Poly(lactic acid) (PLA) is considered to be one of the most promising biodegradable materials in the family of aliphatic polyesters. PLA and its copolymers, such as poly(lactic acid)-co-(glycolic acid), are widely used as biomedical materials or alternatives to petrochemical-based polymers. PLA has the advantage that it is produced commercially by an efficient method at relatively low cost. However, there are some disadvantages to PLA. It is brittle and difficult to functionalize. Blending is an extremely promising approach to improve the properties of polymers. Blends may exhibit the physical and chemical properties of both individual polymers. The miscibility of the two polymers can be evaluated by the glass transition temperature (Tg) method. Different chemical properties, such as optimum hydrophilic/hydrophobic balance and the ability to act as a drug-carrier may be obtained by functionalization of our recently synthesized brominated PLA copolymers. Materials with good mechanical properties may be produced by blending functionalized PLA with high molecular weight commercialized PLA. This study investigates the miscibility of brominated PLA with high molecular weight PLA. The influence of different blends ratios, molecular weights of PLA and configurations of PLA on the miscibility is presented. iii ACKNOWLEDGEMENTS I would like to thank my research advisor Dr. Coleen Pugh for providing me the opportunity and guidance for my research. I am very grateful for her patience and encouragement. I am also grateful to Dr. Li Jia to be my committee member. I would like to thank Dr. Abhishek Banerjee to be my mentor at the beginning of my research. I would like to thank Dr. Robert Weiss and Dr. Allen Padwa for providing the chemical samples and suggestions for research. I would like to thank all of my group members, especially Gladys Montenegro and Cesar Lopez Gonzalez for their help of GPC and DSC. I would also like to thank all my family and friends. iv TABLE OF CONTENTS Page LIST OF TABLES .................................................................................................... vii LIST OF FIGURES ................................................................................................. viii LIST OF SCHEMES ....................................................................................................x CHAPTER I INTRODUCTION .................................................................................................... 1 II POLY(LACTIC ACID) ........................................................................................... 3 2.1 Application ...................................................................................................... 3 2.2 Limitation ........................................................................................................ 4 III THEORIES OF POLYMER MIXTURES ............................................................. 5 3.1 Flory-Huggins Theory .................................................................................... 5 3.2 Fox Equation ................................................................................................... 6 3.3 Gordon-Taylor Equation .................................................................................. 7 IV MISCIBILITY OF PLA-CONTAINING BLENDS .............................................. 8 4.1 PLA blends with Poly(ethy1ene glycol) ......................................................... 8 4.2 PLA Blends with Poly(ε-caprolactone) ........................................................ 12 4.3 PLA Blends with Polyhydroxyalkanoates .................................................... 14 4.4 P(DL)LA Blends with Poly(methyl methacrylate) ....................................... 15 v V EXPERIMENTAL ................................................................................................ 17 5.1 Materials ....................................................................................................... 17 5.2 Instrument ..................................................................................................... 17 5.3 Synthesis of 2-Bromin-3-hydroxypropionic acid ......................................... 18 5.4 Copolymerization of LA and BrH ................................................................ 20 5.5 Hydrolyze PLA ............................................................................................. 21 5.6 Blending ........................................................................................................ 22 VI RESULTS AND DISCUSSION ....................................................................... 23 6.1 Study of different ratio of blends .................................................................. 23 6.2 Study of different molecular weight PLA blends .......................................... 25 6.3 Study of different configuration of PLA ........................................................ 29 6.4 Conclusions .................................................................................................... 31 REFERENCES ......................................................................................................... 32 vi LIST OF TABLES Table Page 1. Results from DSC analysis for the PLA/PEG Blends21 .......................................10 2. Results from DMA for the PLA/PEG Blends21 ...................................................10 3. Mechanical Properties of PLA/PCL/TPP Blends24 ..............................................12 4. Thermal Properties of P[(S)-LA]/ataPHB Blends26 .............................................14 5. Blend ratio of PLA and PL60B40 .........................................................................22 6. Summary of DSC analysis data .........................................................................23 7. GPC and DSC results of hydrolyzed PLA .........................................................25 8. Summary of DSC analysis data .........................................................................26 9. Results of Tg calculated from Fox equation .........................................................28 10. Results of Tg calculated from Gordon-Taylor equation .......................................28 11. Summary of DSC analysis data .........................................................................29 12. Results of Tg calculated from Fox equation .........................................................30 13. Results of Tg calculated from Gordon-Taylor equation .......................................31 vii LIST OF FIGURES Figure Page 1. DSC thermograms of PEG/PLA blends ...............................................................8 2. Phase diagram of PLLA/PEO blends. The dotted line shows the proportional dependence of Tg with the blend composition22 .................................................. 11 3. （A）thermograms in the second heating runs for solution/precipitation DL-PLA/PMMA blends with compositions from 100/0 to 0/100 （B）thermograms in the second heating runs for solution-cast DL-PLA/PMMA blends with compositions from 100/0 to 0/100.27 ................................................16 27 4. Tg versus compositions in solution-cast P(DL)LA/PMMA blends ...................16 5. 1H NMR spectrum of 300 MHz 1H NMR spectrum of 2-bromo-3-hydroxypropionic acid .....................................................................20 1 6. H NMR spectrum of PL60B40..............................................................................21 7. Normalized DSC thermograms in second-heating runs of L-PLA/PL60B40 blends different L-PLA/ PL60B40 ratio (9/1, 8/2, 6/4, 5/5); L-PLA (Nature Works 5 3 PLA6202, 2% D-isomer) Mn = 1.16×10 , PL60B40 Mn = 8.69×10 . ...................23 8. Tg of L-PLA and PL60B40 blends with different weight ratios of L-PLA ...........24 9. L-PLA molecular weight and Tg as a function of hydrolysis time at 60 ℃ in 100% relative humidity. .................................................................................................26 10. Normalized DSC thermograms in second-heating runs of 6/4 L-PLA / PL60B40 blends with different molecular weight L-PLA prepared by hydrolysis (time in hours) of high molecular weight L-PLA (0 h, Nature Works PLA6202, 2% 3 D-isomer); PL60B40 Mn = 8.69×10 . .................................................................27 11. Normalized DSC thermograms in second-heating runs of 6/4 D-PLA/ PL60B40 Blends with different molecular weight DL-PLA prepared by hydrolysis (time in viii 12. hours) of high molecular weight DL-PLA (0 h, Nature Works PLA4060, 10% 3 D-isomer); PL60B40 Mn = 8.69 x 10 . ................................................................30 ii LIST OF SCHEMES Scheme Page 1.