ADVANCED BIOFRIENDLY POLYMERS Hydrolytic degradation and biodegradation of

ADVANCED BIO-FRIENDLY POLYMERS Hydrolytic degradation and biodegradation of polymers Eva Papajová

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

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

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

Ø polyanhydrides Ø polyesters Ø polyamides Ø polyether urethanes Ø polyurea Ø polycarbonates

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

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

Ø 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 Ø structure of the polymer makes it biodegradable

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

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

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

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

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

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

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

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

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

Simulations (reactor) Analysis in the nature Ø water, soil, compost or material from dump Ø complexity of parameters Ø defined conditions Ø water, soil, compost, dump Ø complexity of parameters Ø variability of conditions Relevance of the information Laboratory analysis Ø enzymes, individual and mixed cultures of microorganisms Ø artificial conditions Ø precisely defined conditions

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

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