ADVANCED BIO-FRIENDLY POLYMERS Eva Papajová

Thermal degradation Thermooxidation Photodegradation Photooxidation Hydrolytic degradation Biodegradation Mechanochemical degradation, degradation by O 3, radiolytic degradation, burning

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

Decomposition of polymer chain by reaction with water. Ability of polymers to degrade by hydrolysis is given by difference in electronegativity of atoms in polymer chain or side groups. RX + HOH → ROH + HX

O

 polyanhydrides  polyesters  polyamides  polyethers  polyether urethanes  polyurea  polycarbonates

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

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

 degradation process resulting from the action of naturally occuring microorganisms such as bacteria, fungi and algae microorganisms can use their enzymes for cleavage of the polymer chain at the specific location and use them as a source of energy  structure of the polymer makes it biodegradable

Enzymes responsible for the biodegradation process ENDOCELLULAR ENZYMES EXOGENEOUS CELLULAR ENZYMES 1 st step 2 nd step

EXTRACELLULAR ENZYMES Preliminary degradation (photodegradation, photooxidation, chemical degradation, etc.) enhances biodegradation process. 1 st STEP  enzyme secreted by cell that works outside of that cell  used for cleavage of long polymer chain in order to permeate through cell membrane Cell Depolymerization (oligomers, dimers, monomers,...)

Material changes  Mechanical properties (tensile or dynamic analysis)  Molecular weight of polymer chains (size-exclusion chromatography)  Degradation in crystalline or amorphous region (differential scanning calorimetry)  Structure of polymer material (scanning electron microscopy, contact angle measurements)  Changes in polymer structure (spectroscopy techniques – NMR, IR, MS) - important mostly for characterization of the first step of biodegradation

Enzymes responsible for the biodegradation process ENDOCELLULAR ENZYMES EXOGENEOUS CELLULAR ENZYMES1 st step 2 nd step

Cell ENDOCELLULAR ENZYMES2nd STEP  enzyme works inside the cell in which it was produced  carbon and energy sources are metabolized in presence of O 2 in absence of O 2 CO 2, H 2 O CH 4, CO 2 Mineralization Products

Production of gasses - characteristic for mineralization process Devices for measuring composition of gasses (O 2, CO 2, CH 4 )  Gas chromatography  IR spectroscopy (CO 2 )  Paramagnetic resonance (O 2 )  Measurement of pressure (O 2 )  Amount of absorbed gasses measured by titration technique (CO 2 ) Biodegradation process is dependent on factors....

 Flexibility  Crystallinity  Morphology  Functional groups  Crosslinking  Molecular weight  Copolymers  Blend  Tacticity  Additives Polymer characteristics accessability of water and microogranisms functional groups and additives as an active points for initiation of degradation Exposure conditions Abiotic Biotic  Temperature  Moisture  pH  UV radiation  Extracellular enzymes  Hydrophobicity  Biosurfactants

Lamella Amorphous region Crystallinity of polymers Decreasing rate of degradation Increasing crystallinity Tsuji, H., Miyauchi, S. (2001) Polymer Degradation and Stability 71, 415. Poly(L-lactide)

O (CH 2 ) 5 C O ( ) n poly(ε-caprolactone) (PCL) ) OC O () m CH 2 CH 3 OC O ( CH 2 CH 3 n poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) Biodegradation PCL > PHBV > PBS > PLA Hydrolytic degradationPCL < PHBV < PBS < PLA ) C OO (CH 2 ) 4 C O (CH 2 ) 2 ( O n poly(butylene succinate) (PBS) poly(lactide) (PLA) O CH C O ( n CH 3 ) 5:1 3.5:1 3:11:1

 enzymes, individual and mixed cultures of microorganisms  artificial conditions  precisely defined conditions  water, soil, compost or material from dump  complexity of parameters  defined conditions  water, soil, compost, dump  complexity of parameters  variability of conditions Relevance of the information

 starch  cellulose  pectin  gelatine  poly(hydroxybutyrate)  poly(lactide)  polycaprolactone Biodegradable polymers

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