Please enable JavaScript.
Coggle requires JavaScript to display documents.
Classification of polymers (1- based on the molecular forces (4 factors …
Classification of polymers
3-Origin.
synthetic
man made polymers
biodegradable
used in MR
ex
PLA, PGA, PLGA, PCL, ...
Poly(dioxanone)
Poly(anhydrides)
Poly(trimethylene carbonate)
Polyphosphazenes ...
polyhydroxybutyrate , polyester ,polyamide
breakdown and lose their initial integrity, ex: homo and copolymers of polylactide and polyglycolide are hydrolytically degraded to lactic and glycolic acid which are consequently eliminated via the Krebs cycle as water and carbon dioxide
non-biodegradable
PVP
-> semisolid dispersions
silicone derivatives
ex :
polymethacrylate , polymethyl methacrylate
used in contact lenses , controlled release formulations ,,,
A variety of synthetic polymers as
plastic (polythene), synthetic fibres (nylon) and synthetic rubbers
semisynthetic
chemically modified n.polymers ex : cellulose derivatives : CMC ,HPMC ,methyl cellulose , ethyl cellulose (non-biodegradable )
natural
rubber, silk,starch,proteins etc.)
proteins : collagen , albumin , gelatin , keratin
polysaccharides : alginates , cyclodextrin , chitosan , dextrose , starch , hyalouronic acid , cellulose
DNA/RNA
4- Mode of formation
Addition polymers ( chain growth )
There is simple addition of monomer molecules to each other
without loss of any atoms
from the original monomer molecules.
monomers contain double and triple bonds
Rx
chain propagation
as the radicals react with another molecule of monomers so another bigger size radicals are formed , repetition of this seq carries the Rx forward
chain termination
: the product radical at some stages react with other radical to form polymerized product
chain initiatio
n : the double bond is activatedto produce free radical thus generate new larger free radicals
polyalkenes ex polyethene
free radical governed
Condensation polymers ( step growth )
In this process bond is is established between the molecules, & some of the
atoms in the monomer are lost as a by product compound ( small molecule : water , alcohol )
bifunctional or trifunctional monomers ex cont COOH & Amine --> polyamide
6-Based on structure/shape
Branched : branched monomer molecule ex : isopropyl
Crosslinked & Network structure, which is basically highly cross-linked
These are usually formed from bi-functional and tri-functional monomers and contain strong covalent bonds between various linear polymer chains,
e.g. bakelite, melamine,
mech of cross-linking
chemical
chitosan on addition of TPP ( Na tripolyphosphate ) ionic bonds are formed bet Na and OH- in chitosan & bet negative polyphosphate and positively charged chitosan -->
crosslinked hydrogel --> CR
Na alginate on addition of CaCl2 --> Ca alginate
( ins --> SR )
physical
polyvinyl alc gel by cycles of freezing & thawing
inc conc
pH (CAP )
note hydrogels; which are formed bycross linked water soluble polymers with a network type structure, which swells in water without dissolving
Linear.
consist of long and straight chains.
The examples of Polymers are high density
polythene, polyvinyl chloride :
2-Types of monomers involved in the polymers
Heteropolymers (co-polymer ) more than one monomer
an alternating copolymers.
-a-b-a-b-a-b-
block copolyme
-a-a-a-b-b-b-b-a-a-a-a-b-b-b-
has different menomers in block of individual special.
polaxamer ( polyoxyethylene "hydrophilic " + polyoxypropylene" hydrophobic " )
PLGA ( PLA "water ins " +glycolic acid "water sol" )
a random copolymer
a-a-b-b-a-b-a-b-
a graft copolymer
—a — a — a — a — a — a — a — a | b | b
Homopolymers : all the monomeric units are identical
polystyrene
polyoxyethylene
polyoxypropylene
Polyacrylamide
PVP , PVA , PLA
7-Crystallinity
Crystalline
The crystalline region (crystallite) has an orderly arrangement of molecules. The higher the crystallinity, the harder, stiffer, and less ductile the polymer.
Amorphous
1- based on the molecular forces
fibers اقةي من اول واحد
اول واحد thermoplastic : بيتحول بالحراره ل
elastomer اضعف بوندز
thermosetting بيتحول بالحراره لحاجه مابتدوبش زي البكاليت بيستعملوه في الحلل
4 factors
tensil strength , polymer elastic or tough
mechanical prop
hard dt strong bonds used in packaging
app polymers used in DD
intermolecular bonds ex HB , vander waals
effect of plasticiser : dec viscosity
5-acc to water solubility
hydrophobic
non-polar func gps make them water ins
ethyl cellulose
polydimethylsiloxane
polymethyl methacrylarte (PMMA ) In hard contact lense
hydrophilic
polymers with polar or charged gps ,
soluble
in water
chitosan
HPMC
water insoluble hydrogels
don't dissolve but swell in water , used in sustained release prep
polyhydroxyethyl methyl acrylate (HEMA ) in soft contact lense