1. ADVANCED BIO-FRIENDLY POLYMERS Hydrolytic degradation and biodegradationofpolymers Eva Papajová

2. Typesofpolymerdegradation Mechanochemical degradation, degradation by O3, radiolytic degradation, burning Thermal degradation Thermooxidation Photodegradation Photooxidation Hydrolytic degradation Biodegradation    

3. Hydrolyticdegradation Decomposition of polymer chain by reaction with water. in relation with ester bond of polyesters pH initiated • pH < 7 (acid) • pH > 7 (basic)

4. Hydrolyticdegradationofpolymerchains Decomposition of polymer chain by reaction with water. RX + HOH → ROH + HX Ability of polymers to degrade by hydrolysis is given by difference in electronegativityof atoms in polymer chain or side groups. Heteroatoms in polymer chains provide higher ability for hydrolytic degradation.

5. pH INITIATED HYDROLYSIS Acid hydrolysis + + + Basichydrolysis O + + +

6. Hydrolyticdegradationofpolymerchains • polyanhydrides • polyesters • polyamides • polyethers • polyetherurethanes • polyurea • polycarbonates

7. Hydrolyticdegradationofpolymerchains Depends on • repulsive interactions with ions • availability of reacting bonds • physical parameters (swelling, transport of ions along polymer chain)

8. BIODEGRADATION Water as a carrier of microorganisms for biodegradation of polymer material.

9. Biodegradation • degradationprocessresultingfromtheactionofnaturallyoccuringmicroorganismssuchasbacteria, fungi and algae microorganismscanusetheirenzymesforcleavageofthepolymerchainatthespecificlocation and usethemas a sourceofenergy • structure of the polymer makes it biodegradable

10. Biodegradation Enzymesresponsibleforthebiodegradationprocess EXOGENEOUS CELLULAR ENZYMES 1st step 2nd step ENDOCELLULAR ENZYMES

11. Biodegradation 1st STEP EXTRACELLULAR ENZYMES • enzyme secreted by cell that worksoutside of that cell • used for cleavage of long polymer chain in order to permeate through cellmembrane Depolymerization (oligomers, dimers, monomers,...) Cell Preliminary degradation (photodegradation, photooxidation, chemical degradation,etc.) enhancesbiodegradation process.

12. Evaluation of degradationprocess Materialchanges - important mostly for characterization of the first step of biodegradation • Mechanicalproperties (tensile or dynamicanalysis) • Molecular weight of polymer chains (size-exclusion chromatography) • Degradation in crystalline or amorphous region (differential scanning calorimetry) • Structureofpolymermaterial (scanningelectronmicroscopy, contactanglemeasurements) • Changes in polymer structure (spectroscopy techniques – NMR, IR, MS)

13. Biodegradation Enzymesresponsibleforthebiodegradationprocess EXOGENEOUS CELLULAR ENZYMES 1st step 2nd step ENDOCELLULAR ENZYMES

14. Biodegradation 2nd STEP ENDOCELLULAR ENZYMES • enzyme works inside the cell in which it was produced • carbon and energy sources are metabolized Products Mineralization in presenceof O2 CO2, H2O CH4, CO2 in absenceof O2 Cell

15. Evaluationofdegradationprocess Productionofgasses - characteristic for mineralization process Devices for measuring composition of gasses (O2, CO2, CH4) • Gaschromatography • IR spectroscopy (CO2) • Paramagnetic resonance (O2) • Measurement of pressure (O2) • Amount of absorbed gasses measured by titration technique (CO2) Biodegradation process is dependent on factors....

16. Parametersofdegradationconditions Polymercharacteristics Exposureconditions • Flexibility • Crystallinity • Morphology • Functional groups • Crosslinking • Molecular weight • Copolymers • Blend • Tacticity • Additives Abiotic Biotic • Temperature • Moisture • pH • UV radiation • Extracellular enzymes • Hydrophobicity • Biosurfactants accessabilityofwater and microogranisms functional groups and additives as an active points for initiation of degradation

17. PARAMETERS OF BIODEGRADATION PROCESS Crystallinityofpolymers Poly(L-lactide) Lamella Decreasing rate of degradation Increasing crystallinity Tsuji, H., Miyauchi, S. (2001) Polymer Degradation and Stability 71, 415. Amorphous region

18. PARAMETERS OF BIODEGRADATION PROCESS poly(ε-caprolactone) (PCL) poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) O ( (CH2)5 ) O C n 3.5:1 5:1 poly(butylene succinate) (PBS) poly(lactide) (PLA) O O CH3 CH3 O ) ( O O CH3 CH2 (CH2)4 (CH2)2 O O C C n ) ( O CH C n ( ) ( C CH2 CH2 O C CH2 CH2 O n m ) 3:1 1:1 Hydrolytic degradation PCL < PHBV < PBS < PLA PCL > PHBV > PBS > PLA Biodegradation

19. Biodegradationevaluation • enzymes, individual and mixedculturesofmicroorganisms • artificial conditions • preciselydefinedconditions Laboratoryanalysis • water, soil, compost or materialfromdump • complexityofparameters • definedconditions Relevanceoftheinformation Simulations (reactor) • water, soil, compost, dump • complexityofparameters • variability ofconditions Analysis in thenature

20. bIODEGRADATION Biodegradablepolymers • starch • cellulose • pectin • gelatine • poly(hydroxybutyrate) • poly(lactide) • polycaprolactone

21. Applicationsofbiodegradablepolymers sutures drug delivery systems orthopedic fixation devices replacing a bone cement medicinal mulching foils plant pots silage foils packaging (bags, boxes) tooth brush handles industrial others ...textile, electronics, houseware