Transcript Physical-chemical properties of biopolymer solutions.

LECTURE
Physical-chemical
properties of biopolymer
solutions.
ass. prof. Iryna R. Bekus
BIOPOLYMERS
•
Biopolymers are polymers produced by living
organisms.
•
Since they are polymers, biopolymers contain
monomeric units that are covalently bonded to form
larger structures.
•
There are three main classes of biopolymers based on
the differing monomeric units used and the structure
of the biopolymer formed:
•
polynucleotides, which are long polymers composed
of 13 or more nucleotide monomers;
polypeptides, which are short polymers of amino
acids; and
polysaccharides, which are often linear bonded
polymeric carbohydrate structures.
•
•
Biological role of polymers
•
•
•
•
Biopolymers, have a lot functions:
Catalytic effect– enzymes;
As regulators – hormones;
is the storage and transfer of genetic
information.(DNA);
• Storage energy (Starch, glycogen);
• Protection - immunoglobulin;
• Structural (collagen, keratins, fibril).
CLASSIFICATION HMC
• Polymers are classified by different
possible:
• Classification by source;
• Classification by structure;
• Classification by synthesis;
• Classification by molecular forces.
Classification by source
• Natural
(nucleic
acids,
polysaccharides, protein, natural
rubber (polyisoprene));
• Synthetic
(polyethelene,
teflon,
polyvinilchloride, polystyrene).
Classification by structure
Linear polymers. In these polymers,
the monomers are joined together to
form long straight chains of polymer
molecules. Because of the close
packing of polymer chains, linear
polymers have high melting point,
high densities and high tensile
(pulling) strength.
Branched chain polymers. In these
polymers, the monomer units not
only combine to produce the linear
chain (called the main chain) but
also form branches along the main
chain
Three-dimensional network polymers.
In these polymers, the initially
formed linear polymer chains are
joined together to form а threedimensional network
structure.These polymers are also
called cross-linked polymers
Classification by molecule form
• Globular.
• Fibril.
Classification by nature atoms,
which are in molecule of
polymer
• Carbon contain
polymers
• Hetero polymers
• Element organic
• Inorganic
BIOPOLYMERS AS MATERIALS
•
Some biopolymers- such as
polylactic acid (PLA), naturally
occurring zein, and poly-3hydroxybutyrate can be used as
plastics, replacing the need for
polystyrene or polyethylene based
plastics.
•
Some plastics are now referred to as
being 'degradable', 'oxy-degradable'
or 'UV-degradable'. This means that
they break down when exposed to
light or air, but these plastics are
still primarily (as much as 98 per
cent) oil-based and are not currently
certified as 'biodegradable' under
certain international laws.
•
Biopolymers, however, will break
down and some are suitable for
domestic composting.
Zein is a class of prolamine protein found in maize.
It is usually manufactured as a powder from corn
gluten meal.
Synthesis of
polymers
• Addition
polymerization
occurs when
unsaturated
monomers
react to form а
polymer. It is а
specific type of
addition
reaction.
Condensation
Condensation polymers are formed by the
head-to-tail joining of monomer units. This
is usually accompanied by the loss of а
small molecule, such as water.
Properties
• Properties HMC solution, which same
as true solutions:
• Solutions of high-molecular compounds
are stable as molecular solutions;
• Solutions of high-molecular compounds
are convertible. If high-molecular
compound was solved that the
molecular solution will be farmed. And
if this solution to strip to dryness, so
high-molecular compound was stat,
which can solve again.
• Between high-molecular compound and
solvent has not boundary.
Properties HMC solution, which same
as colloidal solutions:
Size of disperse phase in solutions of highmolecular compounds are same as in
colloidal solutions (10-7 - 10-9 m);
High-molecular compounds can not
permeate through semipermeable
membrane;
High-molecular compounds slowly are
diffused in solutions.
Specific properties HMC solution:
For solutions of high-molecular compounds
are characteristic the swelling and high
viscosity
• Swelling it is process solubility highmolecular compound in solvent.
• Swilling degree (α):
• α = (m – m0)/m0 = mp/m0
• or α = (V – V0)/ V0 = VP / V0
• Where: m0 and V0 – mass or volume
polymer before swilling;
• m and V – mass or volume polymer after
swilling;
• mp, Vp – mass or volume of solvent,
which is absorbed polymer.
• Some time used mass-volume swilling
degree: α= (V0 – V)/ m = cм3/g
BIOPOLYMER USES
• Biopolymers (also called renewable polymers) are produced from
biomass for use in the packaging industry.
• Biomass comes from crops such as sugar beet, potatoes or wheat: when
used to produce biopolymers, these are classified as non food crops.
These can be converted in the following pathways:
• Sugar beet > Glyconic acid > Polyglonic acid
• Starch > (fermentation) > Lactic acid > Polylactic acid (PLA)
• Biomass > (fermentation) > Bioethanol > Ethene > Polyethylene
• Many types of packaging can be made from biopolymers: food trays,
blown starch pellets for shipping fragile goods, thin films for wrapping.
Polylactic acid (PLA)
• One of the few polymers in which the
stereochemical structure can easily be
modified by polymerizing a controlled
mixture of L and D isomers to yield high
molecular weight and amorphous or semicrystalline polymers.
• Properties can be both modified through
the variation of isomers (L/D ratio) and the
homo and (D, L) copolymers relative
contents.
• PLA can be tailored by formulation
involving adding plasticizers, other
biopolymers, fillers, etc
Polylactic acid (PLA)
Bacterial fermentation is used to produce lactic acid from corn starch or cane sugar.
Two lactic acid molecules undergo a single esterfication and then catalytically cyclized to
make a cyclic lactide ester.
PLA of high molecular weight is produced from the dilactate ester by ring-opening
polymerization.
Polymerization of a racemic mixture of L- and D-lactides usually leads to the synthesis
of poly-DL-lactide (PDLLA) which is amorphous.
Stannous octonate
Or tin(II) chloride
Catalytic and thermolytic ring-opening polymerization of lactide (left) to polylactide (right)
Polylactic acid (PLA): Biodegradability
•PLA is considered both as biodegradable (e.g. adapted for shortterm packaging) and as biocompatible in contact with living
tissues (e.g. for biomedical applications such as implants, sutures,
drug encapsulation, etc.).
•PLA can be degraded by abiotic degradation (i.e. simple
hydrolysis of the ester bond without requiring the presence of
enzymes to catalyze it). During the biodegradation process, and
only in a second step, the enzymes degrade the residual oligomers
till final mineralization (biotic degradation).
•As long as the basic monomers (lactic acid) are produced from
renewable resources (carbohydrates) by fermentation, PLA
complies with the rising worldwide concept of sustainable
development and is classified as an environmentally friendly
material.
Due to PLA's relatively low glass
transition temperature, PLA cups
cannot hold hot liquids. However,
much research is devoted to
developing a heat resistant PLA
Biodegradable cups at a restaurant
Mulch film made of polylactic
acid (PLA)-blend bio-flex
Proteins by Function
O
H2N
R
N
H
OH
O
O
H2N
R
N
H
OH
O
O
H2N
R
N
H
OH
O
Polysaccharides
• Polymers composed
of sugars
• Similar to synthetic
polymers in that
primary structure,
DP not as fixed as
proteins
• Uses include
energy storage,
component of extra
cellular matrix
(hyaluronan)
Acidic Polysaccharides
Acidic polysaccharides are a group of
poly saccharides that contain carboxyl
groups and/or sulfonic esters.
These compounds play an important roles
in structure and function of connective
tissues. These tissues form the matrix
between organs and cells that provides
mechanical strength as well filtering the
flow of molecular information between
cells.
Many connective tissues are made up of
collagen, a structural protein, in
combination with an assortment of acidic
polysaccharides that interact with collagen
to form loose or tight networks.
Hyaluronic acid
Hyaluronic acid is the simplest
acidic polysaccharide present in
connective tissue
MW of ~ 105 and 107 g/mol and
contains 30.000 to 100,000
Found in embryonic tissues and
specialized connective tissues such
as synovial fluid, the lubricant of
joints in the body, and the vitreous
humor of the eye where it provides a
clear, elastic gel that maintains the
retina in proper position.
Swelling and Collapse
of Single Polymer Molecules and Gels
Single polymer molecules
Coil-globule transition
If polymer chains are not ideal, interactions of non-neighboring
monomer units ( the
so-called volume interactions ) should be
taken into account. If these interactions are repulsive, the coil swells
with respect to its ideal dimensions. If monomer units attract each
other, contraction leads to the “condensation” of polymer chain upon
itself with the formation of a ”dense droplet” conformation, which is
called a polymer globule.
synthetic polymers
Polymers made in industry
from chemical substances
Scientists are able to copy
structures of natural
polymers to produce synthetic
polymers trough scientific
research
synthetic polymers
many of raw materials for
synthetic polymers are obtain
from
-> petroleum
types of synthetic polymers
 plastics
 fibers
 elastomers
plastics
Properties of plastics :




Light
strong
malleable
inert to chemical
insulators of electricity
and heat
fibers
long chain polymers that
withstand stretching
example of fibers are :polyamide nylon,
terylene
phenol-formaldehyde (PF)
acrylic polymers
elastomers
polymer that can regain its
original shape after being
stretched or pressed
example of elastomers are :Styrene-butadiene rubber(SBR)
Polyisoprene (IR)
Polybutadiene (BR)
Chloroprene Rubber (CR)
What are the properties of plastics?
Plastics are all different, but they show a few general
properties:
 they do not conduct electricity and are poor
conductors of heat
 they are unreactive – most are not affected by water or
air, and many are not affected by chemicals.
Why is the unreactivity of plastics both useful and
problematic?
Their unreactivity makes plastics durable and able to safely
contain and protect many substances. However, it also
means that they persist in the environment for a long time.
Physical properties of polymers are
governed by three main factors:
• Number of monomer units in the chain, N,
is large: N >> 1.
• Monomer units are connected in the chain.
 They do not have the freedom of
independent motion (unlike systems of
disconnected particles, e.g. low molecular
gases and liquids).  Polymer systems are
poor in entropy.
• Polymer chains are generally flexible.
What makes plastics different?
The properties of a plastics depend greatly on how the
polymer chains are arranged:
 branching chains
make plastics
light, soft and
easy to melt
(e.g. low-density
polyethene)
 lined-up chains
make plastics
dense, rigid and
harder to melt
(e.g. high-density
polyethene).
Changing the properties of plastics
What factors might determine the properties of a plastics?
Factor
Effect
reaction
conditions
Temperature, pressure and catalysts
affect the length and branching of the
polymer chain.
monomer
The type of monomer used affects the
type of forces between polymer chains.
additives
Additives can ‘lubricate’ polymer
chains, join them together with crosslinks, or preserve them from decay.
What happens to plastics in landfill sites?
Plastic bags are a major source of
waste at landfill. British shoppers use
over 8 billion of them a year!
The UK has 4,000 landfill sites and it is
predicted that the largest of these will
become full in less than 5 years.
Landfill is a convenient method of waste
disposal but it is only designed to bury
rubbish, not to break it down.
Most plastics are made up of tightly
bonded molecules that cannot be
decomposed by micro-organisms.
These will remain buried at landfill sites
for thousands of years without rotting.
Thank you for attention