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Lactic Acid Polymers and Copolymers: Structure-Property Relationships

This study explores the structure-property relationships of lactic acid polymers and copolymers, focusing on approaches to improve their properties. Topics include synthesis methods, purification techniques, and the incorporation of comonomers for enhanced properties.

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Lactic Acid Polymers and Copolymers: Structure-Property Relationships

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  1. L(+) LACTIC ACID POLYMERS AND COPOLYMERS : STRUCTURE –PROPERTY RELATIONSHIPS Dr. S. Sivaram National Chemical Laboratory,Pune-411 008, INDIATel : 0091 20 2590 2600Fax : 0091 20 2590 2601Email : s.sivaram@ncl.res.inVisit us at : http://www.ncl-india.org 2nd Federation of Asian Polymer Societies Polymer Congress, Beijing, China May 11 , 2011

  2. PLLA : MAJOR PROPERTY DEFICITS • Slow rate of crystallization • Very brittle material ; Elongation : 3-4 %, • Poor heat stability • Poor chain entanglement in melt state leading to poor melt viscosities CSIR Proprietary

  3. PLLA PROPERTY IMPROVEMENTS : APPROACHES • Poor rate of crystallization • Annealing and cold crystallization • Nucleation • Poor Elongation • Plasticization • Copolymerization • Increase Tm • Stereocomplexation • Copolymerization • Nanocomposites and blends • Increase melt viscosity • Crosslinking • Branching

  4. SYNTHESIS OF POLY (L+) LACTIC ACID)S FROM L(+) LACTIC ACID

  5. Poly(L-Lactic acid) oligomers Dehydro-polycondensation L-Lactic acid Depolymerization & cyclization Ring opening polymerization L-lactide 95% yield, mp =94oC Optical purity 100% Poly(L-Lactic acid) s POLY(L+) (LACTIC ACID)S (PLLA) : PREPARATION

  6. CRUDE L(+) LACTIDEFORMATION SUGAR CANE FERMENTATION OF SUGAR CANE JUICE TO L(+) LA ROP L(+) LACTIDE CRYSTALS L(+) LACTIDE CRYSTALLIZATION

  7. LABORATORY POLYMERIZATION SET -UP • Polycondensation set up doubled up to do distillation. • SS reactor of 200mL / 800 mL. • Electrical heating and overhead stirring. • Ability to purge, pull vacuum, add additives. • Nozzle at bottom to extrude polymer melt coupled with a pelletizer.

  8. PREPARATION OF L(+) LA OLIGOMER VIA DEHYDRO-POLYCONDENSATION Lactic acid : 600 g (90% aqueous solution) Conditions : 150oC/N2/2h, 150oC/100 mm, Hg/1.5h, 150oC/30 mm, Hg/1.5h, 150oC/0.005 mm, Hg/1h * Determined by GPC in chloroform Under these conditions only linear oligomers are obtained with no cyclic oligomers ( MALDI-TOF)

  9. PREPARATION OF DILACTIDE VIA DEPOLYMERIZATION AND CYCLIZATION) Lactic acid oligomer : 493 g; Catalyst : Tin powder (<150 m) Conditions : 160oC/N2/1h, 180oC/100 mm, Hg/1h, 190oC/10 mm, Hg/1h, 200oC/0.01 mm, Hg/2h L(+) LACTIDE AS FORMED UNSUITABLE FOR POLYMERIZATION:PURIFIED BY CRYSTALLIZATION FROM MELT :

  10. PROTON NMR OF CRUDE L(+)LACTIDE PURIFICATION NCL PURAC

  11. PROTON NMR OF CRYSTALLIZED L(+) LACTIDE NCL PURAC

  12. PREPARATION OF POLY(LACTIC ACID)S via RING OPENING POLYMERIZATION • Catalyst concentration: 0.03% to 0.05 wt% • Chain stopper : Lauryl alcohol • Temperature: 180oC

  13. ISOSORBIDE AS A COMONOMER

  14. ISOSORBIDE MONOMER Dihydrohexitols - byproducts of biomass - prepared from starch, chiral in nature - thermally stable Monomer for biodegradable polymers - improved accessibility of two -OH groups - exo substituent increases ring thermal stability Polymers presented promising properties - high glass transitions - excellent thermal stabilities - interesting physical properties Isosorbidecopolyesters - relatively high Tg’s - cholesteric phase formation

  15. ISOSORBIDE: A PLATFORM CHEMICAL

  16. L(+) LA- ISOSORBIDE COPOLYMER Incorporation of isosorbide into PLLA by melt/solution disproportionation followed by solid state polymerization

  17. L(+) LA-ISOSORBIDE COPOLYMER VIA MELT DISPROPORTIONATION PLLA : 10 g (IV : 1.6 dL/g; Mw: 160,000 g/mol) Catalyst : Titanium isopropoxide Catalyst conc.: 0.5 wt% (based on PLA) * Determined in chloroform at 30oC by Ubbelhode viscometer.

  18. DISPROPORTIONATED L(+)LA-ISOSORBIDE COPOLYMER IV was determined in Chloroform at 30oC by Ubbelhode viscometer Tg, Tm, Tc were determined by Q10 DSC (TA Instruments).

  19. L(+) LA-ISOSORBIDE COPOLYMER VIA SOLUTION DISPROPORTIONATION PLLA : 10 g (IV : 1.6 dL/g; Mw: 160, 000 g/mol) Solvent : Chloroform Catalyst : Titanium isopropoxide Catalyst conc.: 0.5 wt% (based on PLA) * Determined in chloroform at 30oC by Ubbelhode viscometer.

  20. DISPROPORTIONATED L(+)LA-ISOSORBIDE COPOLYMER IV was determined in Chloroform at 30oC by Ubbelhode viscometer Tg, Tm, Tc were determined by Q10 DSC (TA Instruments).

  21. 1H NMR SPECTRA OF ISOSORBIDE IN CDCL3 Fig. 2

  22. 1H NMR SPECTRA OF PLA-ISOSORBIDE COPOLYMER IN CDCL3 2 3,8 1 7,4 6,5 3,8 6,5 7,4  ppm

  23. 1H NMR SPECTRA OF PLA-ISOSORBIDE COPOLYMER IN CDCL3

  24. SOLID STATE POLYMERIZATION OF DISPROPORTIONATED L(+) LA-ISOSORBIDE COPOLYMER IV was determined in Chloroform at 30oC by Ubbelhode viscometer Tg, Tm, Tc were determined by Q10 DSC (TA Instruments).

  25. :DSC THERMOGRAMS OF PLA-ISOSORBIDE COPOLYMER DURING SSP Fig. 9

  26. 12-HYDROXY STEARIC ACID AS COMONOMER

  27. COPOLYMERS OF L (+) -LACTIC ACID WITH 12-HYDROXY STEARIC ACID

  28. PROPERTIES OF L(+) LA – 12- HSA COPOLYMERS

  29. BRANCHING/CROSSLINKING USING STYRENE –GMA COPOLYMER

  30. SYNTHESIS OF STYRENE-GMA COPOLYMER aDetermined by Ubbelhode viscometer in chloroform at 30oC. bDetermined by gel permeation chromatography using chloroform solvent. cDetermined by 1H NMR spectroscopy. dDetermined by titrimetry.

  31. MELT COMPOUNDING AND RHEOLOGICAL MEASUREMENTS Temp. : 180oC, Residence Time : 3 min in nitrogen Speed : 100 rpm DSM MICROCOMPOUNDER ARES RHEOMETER

  32. MELT COMPOUNDING OF STYRENE-GMA COPOLYMER WITH PLLA aDetermined by gel permeation chromatography using chloroform solvent.

  33. STORAGE MODULUS AND COMPLEX VISCOSITY OF PLLA- GMA BLENDS Addition of 2 % GMA enhances melt viscosity of PLLA

  34. SUMMARY • Tm improved using isosorbide as comonomer • Tg decreased using 12- hydroxystearic acid as comonomer • Branching and crosslinking with S-GMA copolymer improves melt viscosity of PLLA

  35. THANK YOU

  36. H Oct Sn O R 2 O H ROCO(CH )OCOCH(CH )O SnOct O 3 3 2 O O SYNTHESIS OF PLLA OLIGOMERS CONTROLLED END GROUPS • Controlled ROP of purified LL-dilactide performed 120 °C/ 12 h R = H, WATER used as initiator to get carboxylic acid end groups Mn = ([M] / [I]) x MLactide x conversion % and DPn = ([M] / [I]) x conversion %

  37. MOLECULAR WEIGHT DETERMIATION OF PLLA SAMPLES Fig. 3.1: 13C-NMR spectrum (500 MHz) of PLLA oligomer 3.1 synthesized by ROP : Inset showing ester carbonyl region (ester as well as carboxylic acid)

  38. DSC OF PLA OLIGOMERS HAVING HYDROXYLA AND CARBOXY END GROUPS Fig. 3.2: Thermal characterization (DSC) first and second heating showing Tm and Tg, respectively of PLA oligomers: (a) 3.1, first heating; (b) 3.2, first heating; (c) 3.1, second heating and (d) 3.2, second heating

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