ADVANCED BIO-FRIENDLY POLYMERS

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ADVANCED BIO-FRIENDLY POLYMERS
Hydrolytic degradation and biodegradation of
polymers
Eva Papajová
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Types of polymer degradation
Mechanochemical degradation, degradation by O3,
radiolytic degradation, burning
Thermal degradation Thermooxidation Photodegradat
ion Photooxidation Hydrolytic degradation Biodegra
dation
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Hydrolytic degradation
Decomposition of polymer chain by reaction with
water.
in relation with ester bond
of polyesters
pH initiated

• pH lt 7 (acid)
• pH gt 7 (basic)

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Hydrolytic degradation of polymer chains
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.
Heteroatoms in polymer chains provide higher
ability for hydrolytic degradation.
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pH INITIATED HYDROLYSIS
Acid hydrolysis



Basic hydrolysis
O



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Hydrolytic degradation of polymer chains

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

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Hydrolytic degradation of polymer chains
Depends on

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

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

• 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

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Biodegradation
Enzymes responsible for the biodegradation process
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Biodegradation
EXTRACELLULAR ENZYMES
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

Depolymerization (oligomers, dimers, monomers,
...)
Cell
Preliminary degradation (photodegradation,
photooxidation, chemical degradation, etc.)
enhances biodegradation process.
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Evaluation of degradation process
Material changes
- important mostly for characterization of the
first step of biodegradation

• 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)

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Biodegradation
Enzymes responsible for the biodegradation process
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Biodegradation
ENDOCELLULAR ENZYMES
2nd STEP

• enzyme works inside the cell in which it was
  produced
• carbon and energy sources are metabolized

Products
Mineralization
in presence of O2
CO2, H2O
in absence of O2
CH4, CO2
Cell
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Evaluation of degradation process
Production 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)

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Parameters of degradation conditions
Polymer characteristics
Exposure conditions

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

Abiotic
Biotic

• Temperature
• Moisture
• pH
• UV radiation

• Extracellular enzymes
• Hydrophobicity
• Biosurfactants

accessability of water and microogranisms function
al groups and additives as an active points for
initiation of degradation
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PARAMETERS OF BIODEGRADATION PROCESS
Crystallinity of polymers
Lamella
Amorphous region
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PARAMETERS OF BIODEGRADATION PROCESS
poly(e-caprolactone) (PCL)
poly(3-hydroxybutyrate-co-3-hydroxyvalerate)
(PHBV)
poly(butylene succinate) (PBS)
poly(lactide) (PLA)
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Biodegradation evaluation

• enzymes, individual and mixed cultures of
  microorganisms
• artificial conditions
• precisely defined conditions

Laboratory analysis

• water, soil, compost or material from dump
• complexity of parameters
• defined conditions

Simulations (reactor)

• water, soil, compost, dump
• complexity of parameters
• variability of conditions

Analysis in the nature
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bIODEGRADATION
Biodegradable polymers

• starch
• cellulose
• pectin
• gelatine
• poly(hydroxybutyrate)
• poly(lactide)
• polycaprolactone

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Applications of biodegradable polymers
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