e.g. polyethene. Sometimes brackets
are used in polymer names to indicate the repeated unit, e.g.
poly(ethene).
polyacrylamide A polymer
formed from 2-propenamide
(CH 2 :CHCONH 2 ). Polyacrylamide gels
are made using a cross-linking agent
to form three-dimensional matrices.
They are used in gel electrophoresis
(see page).
polyacrylamide gel electrophoresis See page.
polyamide A type of condensation
polymer produced by the interaction
of an amino group of one molecule
and a carboxylic acid group of another molecule to give a protein-like
structure. The polyamide chains are
linked together by hydrogen bonding.
polyatomic molecule A molecule
formed from several atoms (e.g. pyridine, C 5 H 5 N, or dinitrogen tetroxide,
N 2 O 4 ), as distinguished from diatomic and monatomic molecules.
polybasic acid An acid with more
than one replaceable hydrogen atom.
Examples include the dibasic sulphuric acid (H 2 SO 4 ) and tribasic phosphoric(V) (orthophosphoric) acid
(H 3 PO 4 ). Replacement of all the hydrogens by metal atoms forms normal salts. If not all the hydrogens are
replaced, *acid salts are formed.
polychlorinated biphenyl (PCB)
Any of a number of derivatives of
biphenyl (C 6 H 5 C 6 H 5 ) in which some
of the hydrogen atoms on the benzene rings have been replaced by
chlorine atoms. Polychlorinated
biphenyls are used in the manufacture of certain polymers as electrical
insulators. They are highly toxic and
are suspected to be carcinogenic;
their increasing use has caused concern because they have been shown
to accumulate in the food chain.
polychloroethene (PVC; polyvinyl
chloride) A tough white solid material, which softens with the application of a plasticizer, manufactured
from chloroethene by heating in an
inert solvent using benzoyl peroxide
as an initiator, or by the free-radical
mechanism initiated by heating
chloroethene in water with potassium persulphate or hydrogen peroxide. The polymer is used in a variety
of ways, being easy to colour and resistant to Üre, chemicals, and
weather.
polycyclic Denoting a compound
that has two or more rings in its molecules. Polycyclic compounds may
contain single rings (as in phenylbenzene, C 6 H 5 .C 6 H 5 ) or fused rings (as in
naphthalene, C 10 H 8 ).
polydioxoboric(III) acid See boric
acid.
polyene An unsaturated hydrocarbon that contains two or more double carbon–carbon bonds in its
molecule.
polyester A condensation polymer
formed by the interaction of polyhydric alcohols and polybasic acids.
Linear polyesters are saturated thermoplastics and linked by dipole–
dipole attraction as the carbonyl
groups are polarized. They are extensively used as Übres (e.g. Terylene).
Unsaturated polyesters readily
copolymerize to give thermosetting
products. They are used in the manufacture of glass-Übre products. See also
alkyd resin.
polyethene (polyethylene; polythene) A Ûexible waxy translucent
polyalkene thermoplastic made in a
variety of ways producing a polymer
of varying characteristics. In the ICI
process, ethene containing a trace of
427
polyethene
p
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are used in polymer names to indicate the repeated unit, e.g.
poly(ethene).
polyacrylamide A polymer
formed from 2-propenamide
(CH 2 :CHCONH 2 ). Polyacrylamide gels
are made using a cross-linking agent
to form three-dimensional matrices.
They are used in gel electrophoresis
(see page).
polyacrylamide gel electrophoresis See page.
polyamide A type of condensation
polymer produced by the interaction
of an amino group of one molecule
and a carboxylic acid group of another molecule to give a protein-like
structure. The polyamide chains are
linked together by hydrogen bonding.
polyatomic molecule A molecule
formed from several atoms (e.g. pyridine, C 5 H 5 N, or dinitrogen tetroxide,
N 2 O 4 ), as distinguished from diatomic and monatomic molecules.
polybasic acid An acid with more
than one replaceable hydrogen atom.
Examples include the dibasic sulphuric acid (H 2 SO 4 ) and tribasic phosphoric(V) (orthophosphoric) acid
(H 3 PO 4 ). Replacement of all the hydrogens by metal atoms forms normal salts. If not all the hydrogens are
replaced, *acid salts are formed.
polychlorinated biphenyl (PCB)
Any of a number of derivatives of
biphenyl (C 6 H 5 C 6 H 5 ) in which some
of the hydrogen atoms on the benzene rings have been replaced by
chlorine atoms. Polychlorinated
biphenyls are used in the manufacture of certain polymers as electrical
insulators. They are highly toxic and
are suspected to be carcinogenic;
their increasing use has caused concern because they have been shown
to accumulate in the food chain.
polychloroethene (PVC; polyvinyl
chloride) A tough white solid material, which softens with the application of a plasticizer, manufactured
from chloroethene by heating in an
inert solvent using benzoyl peroxide
as an initiator, or by the free-radical
mechanism initiated by heating
chloroethene in water with potassium persulphate or hydrogen peroxide. The polymer is used in a variety
of ways, being easy to colour and resistant to Üre, chemicals, and
weather.
polycyclic Denoting a compound
that has two or more rings in its molecules. Polycyclic compounds may
contain single rings (as in phenylbenzene, C 6 H 5 .C 6 H 5 ) or fused rings (as in
naphthalene, C 10 H 8 ).
polydioxoboric(III) acid See boric
acid.
polyene An unsaturated hydrocarbon that contains two or more double carbon–carbon bonds in its
molecule.
polyester A condensation polymer
formed by the interaction of polyhydric alcohols and polybasic acids.
Linear polyesters are saturated thermoplastics and linked by dipole–
dipole attraction as the carbonyl
groups are polarized. They are extensively used as Übres (e.g. Terylene).
Unsaturated polyesters readily
copolymerize to give thermosetting
products. They are used in the manufacture of glass-Übre products. See also
alkyd resin.
polyethene (polyethylene; polythene) A Ûexible waxy translucent
polyalkene thermoplastic made in a
variety of ways producing a polymer
of varying characteristics. In the ICI
process, ethene containing a trace of
427
polyethene
p
www.AzShimi.ir www.AzShimi.com