ADVANCED BIO-FRIENDLY POLYMERS

Eva Papajová

Thermal degradation

Thermooxidation

Photodegradation

Photooxidation

Hydrolytic degradation

Biodegradation

Mechanochemical degradation, degradation by O3, radiolytic degradation, burning

pH initiated

Decomposition of polymer chain by reaction with water.

in relation with ester bond of polyestersRO

O R'

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

5

O

X R2

R1

H+

+H2O

CX+

O

R1

R2

H2OO

OH

R1

+ XHR2

+ H+

+ OH- H2O H2O

O

OH

R1

+ XHR2

+ OH-

C+X

OH

R1

R2

OH

OO

X R2

R1

O

O

O

O HOH+ H2O +

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 1st step

2nd step

EXTRACELLULAR ENZYMES

Preliminary degradation (photodegradation, photooxidation, chemical degradation, etc.)

enhances biodegradation process.

1st 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 changesMaterial 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 ENZYMES 1st step

2nd step

Cell

ENDOCELLULAR ENZYMES2nd STEP

enzyme works inside the cell in which it was produced

carbon and energy sources are metabolized

in presence of O2

in absence of O2

CO2, H2O

CH4, CO2

Mineralization Products

Production of gassesProduction of gasses

- characteristic for mineralization process

Devices for measuring composition of gasses (O2, CO2, CH4)

Gas chromatography

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 ....Biodegradation process is dependent on factors ....

Flexibility Crystallinity Morphology Functional groups Crosslinking Molecular weight Copolymers Blend Tacticity Additives

Polymer characteristicsPolymer characteristics

accessability of water and microogranismsfunctional groups and additives as an active points for initiation of degradation

Exposure conditionsExposure conditions

AbioticAbiotic BioticBiotic

Temperature Moisture pH UV radiation

Extracellular enzymes Hydrophobicity Biosurfactants

Lamella

Amorphous region

Crystallinity of polymersCrystallinity of polymers

Dec

reas

ing

rate

of

degr

adat

ion

Increasing crystallinity

Tsuji, H., Miyauchi, S. (2001) Polymer Degradation and Stability 71, 415.

Poly(L-lactide)

O (CH2)5 C

O

( )n

poly(ε-caprolactone) (PCL)

)OC

O

( )m

CH2 CH2

CH3

OC

O

( CH2 CH2

CH2

CH3

n

poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)

Biodegradation PCL > PHBV > PBS > PLA

Hydrolytic degradation PCL < PHBV < PBS < PLA

)COO (CH2)4 C

O

(CH2)2(

O

n

poly(butylene succinate) (PBS) poly(lactide) (PLA)

O CH C

O

(n

CH3

)

5:13.5:1

3:1 1:1

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

Rele

vanc

e of

the

info

rmati

on

Biodegradable polymersBiodegradable polymers

medicinalmedicinal sutures drug delivery systems orthopedic fixation devices replacing a bone cement

industrialindustrial mulching foilsplant potssilage foilspackaging (bags, boxes)tooth brush handles

othersothers ... textile, electronics, houseware