Optical Tweezers for Pulling Polymer Chains

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POLYMER Tg(oC) Polydimethylsiloxane
-123 Poly(vinyl acetate)
28 Polystyrene 100 Poly(methyl
methacrylate)
105 Polycarbonate 150 Polysulfone
190 Poly(2,6-dimethyl-1,4-phenylene oxide) 220
Polymers with more flexible backbones, and
smaller substituent side groups have lower glass
transition temperatures
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For semi-crystalline polymers Tg Tm
(oC) Polyethylene (high density) -120 135 Polycapr
olactone -60 61 Poly(vinylidene
fluoride) -45 172 Polyoxymethylene -85 195 Poly(
vinyl alcohol) 85 258 Nylon-6,6
49 265 Poly(ethylene terephthalate) 69 265
Both Tg and Tm increase with decreasing chain
flexibility
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From Fried, Joel R., Polymer Science and
Technology, Prentice Hall PTR, Englewood Cliffs,
NJ (1995)
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From Fried, Joel R., Polymer Science and
Technology, Prentice Hall PTR, Englewood Cliffs,
NJ (1995)
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From Fried, Joel R., Polymer Science and
Technology, Prentice Hall PTR, Englewood Cliffs,
NJ (1995)
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Polymer solutions dilute, semi-dilute, through
to concentrated
Rheology a study of the flow of polymer melts
and solutions (shear-thinning, die swell,
energy requirements for mold filling, design of
mixers, extruders

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Block copolymer solutions and melts making
patterned surfaces and ordered melt morphologies
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Scientists, academics lt 1930s
Industrialists

• 1830 Charles Goodyear, vulcanised
• rubber
• Hevea brasiliensis D S
• elastomeric material
• 1847 Christian Schonbern
• Cellulose nitric acid
• cellulose nitrate
• 1860 Leo Baekeland (Bakelite)
• phenol-formaldehyde resin
• 1930s DuPont (USA) nylon, teflon
• Dow (USA) polystyrene
• 1939 ICI (UK) LDPE
• WWII shortage of natural rubber!

A damned gooey mess
Another failed synthesis
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Scientists begin to look at complex systems . . .
.
1920s Hermann Staudinger, German Physical
Chemist long-chained molecules or
macromolecules interacting, separate
very long, alkane-like intermediate
species but misunderstood . e.g., Tm, flow
behaviour flexibility
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Synthesis of polymers
biosynthesis step-growth polymerisation All
monomer/oligomers/polymers are equally reactive
with one another so that there is a distribution
of chain sizes chain-growth
polymerisation Monomers joined successively to a
growing chain A few long chains in a sea of
monomers
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Step-growth polymerisation
An Am -gt Anm by-product polydispersity
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Chain-growth polymerisation
An A -gt An1 Monodisperse, high-MW of
chains
Initiation of the active monomer
Propagation of growth of the active (free radical
) chain by sequential addition of monomer
Termination of the active chain to give final
product
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Q8 Contrast step-growth and chain-growth
mechanisms in the synthesis of linear polymers
and include statements comparing the final
products of these two classes of synthetic
mechanisms.