macromolecular chemistry s112003 -...
TRANSCRIPT
Supporting material for students registered to subject:
Macromolecular chemistry S112003
Teacher: Jan Merna, Department of Polymers, Institute of Chemical Technology ,Prague
Lecture authored by Jan Merna is licensed under a Creative Commons Attribution-
NonCommercial-NoDerivs 3.0 Unported License
Sources:
Prokopová I.: Makromolekulární chemie, VŠCHT Praha, 2007. (educational text in Czech)
Merna J.: Polymers Instantly, educational text in English, freely accessible from
http://merna.eu/teaching/macromolecular-chemistry/
Encyclopedia of Polymer Science and Technology, J.Wiley Sons, Interscience, Publ., New York, 1964-1991
non-oriented
fringed micelle model
Semi-crystalline polymers:
Amorphous polymers : macromolecules are randomly entangled
Semi crystalline polymers: some degree of regulararrangement of macromolecules
oriented(fiber drawing)
Supramolecular (physical) polymer structure-polymer morphology
Structural requirements for crystalline polymers
•Polymer chain regularity
•Polymer chain flexibility
•Intermolecular interactions
flat lamellae pyramidal lamellae
~ 103 ÅExtended Polymer chain
(from diluted polymer solutions)
Folded chain model
Structure of polymer monocrystal
Spherulite
View in polarization microscope
Dendrit
lamellae branching
Chains orientationin lamellea
Maltesian cross
Irregular crystallite growth from edges/corners
Polymer crystallization from melt or concentrated solutions
Morphology
Chain folding
Shish-kebab(crystallization under stress)
Fringed micellesmodelspherulite
Effect of crystallinity on:
•Mechanical properties (LDPE vs. HDPE): tensile modulustensile strengthHardness
•Thermal properties (PE):Melting temperature
•Optical properties (PS vs. PE): transparency- opacity•(fillers, two amorphous phases - HI PS, foamed PS)
Thermal motions of macromolecules or their segments:
1. Translational motion of entire molecules-flow
2. Motion of macromolecule segment-elasticity
3. Motion of few atoms in main chain or in side groups
4. Equilibrium vibrations of atoms
Glass transition temperature-Tg
glassy-rubbery state
Change of polymer properties (mechanical, refractive index, specific volume)
Determines the application of polymer
Motions 1. and 2. are frozen below Tg
Thermal behaviour of polymers
Amorphous polymerglass transition temperature Tg
flow temperature Tf
Crystalline polymer (hypothetically 100%)melting temperature Tm
Semi-crystalline polymerglass transition temperature flow temperaturemelting temperature
Thermal behavior of polymers- Limit temperatures
Factors influencing Tg
1.Free volume of the polymer: vf
The higher vf the lower Tg
2. Attractive forces between macromolecules
3. Internal mobility of polymer chains - stifness of the chain
4. Molar mass
Determination of Tg
Temperature dependece of thermodynamic property
e.g. specific volume vs. T
Tg change in slope, dv/dT vs. T –discontinuous-second order tdn. transitionTm-discontinuous, first order tdn. transition
Plasticizers
Polymer behavior above Tg
vsp a
Tg TTg´
b
Dependence of specific volume of amorphous polymer on temperature and reaching glass transition temperatureduring fast (a) and slow (b) cooling of polymer sample
Release of macro-Brownian movement in macromolecules
Rubbery state (viscoelastic)
Plastic state, tj. viscous fluid
Flow temper.Tf
Release of movements of macromolecules
Polymer behavior below Tg
„frozen“ segment movement, polymer is in glassy state
Thermal behavior of amorphous polymers
stress
relaxation
Polymer above Tg
Suffcient DP-physical interactions-entenglementsEntropic elasticity
Principle of rubbery elasticity
Thermal behavior of crystalline polymers
a – totally amorphousb – partially crystallinec - hypotetical 100 % crystalline
Tg Tm,b Tm,cT
vsp
abc
Thermodynamics of melting
dGm=dHm-TdSm
Tm=dHm/dSm
Hm ~ intermolecular interactionsdSm~ stiffness of the chain, molar mass
Tg Tm Tf T
E (Pa)
glass
rubber
liquid
109
106
103
Temperature dependence of flexural moduleof partially crystalline polymer
Melting temperatures of selected polymers
> 500
135
308
190
265
CH2 CH
2
CH2
CH2
CCl2
CH(OH) CH2
Polyethylene (HDPE)
syndiotactic
Poly(p-xylylene)
Poly(p-phenylene)
Poly(vinylidenchloride
Poly(vinylcohol)
Tm [°C]
plasticselastomers fibers
polymer dispersionsvarnish/paints
glue
thermoplasticsreactoplastics
thermoplasticelastomers
Clasification of polymers according to properties and applications
Conditions of monomers polymerizability
•Chemical- functionality >2 (fct. groups, multiple bonds, cycles)
•Kinetic-monomer activation: bond polarization+resonance stabilization of product
Rp>Rt (Rtr)
•Thermodynamic aspects
monomer (m) polymer (p)kp
kdp
Thermodynamic aspects
Pn* + M Pn+1*
kp
kdp
K=1/[Me]
dGmp=-RT lnK
Termination + transfer neglected
dGmp=dHmp-TdSmp
Tc=dHmp/dSmpCeiling temperature
No depolymerization of terminated chains
dSmp= -100 to -120 JK-1mol-1
Independent on monomer structure
dHmp:
•Differences in resonance stabilization of monomer and polymer
•Difference in steric tension in monomer and polymer
•Difference in non-bonding interaction in monomer and polymer
Monomer -Hmp (kJ/mol)
ethylene............................................... 101,5
vinylchloride....................................... 111,5
vinylacetate........................................... 89,5
propylene............................................... 85,9
methylacrylate....................................... 84,5
acrylonitrile.......................................... 77,5
vinylidenechloride................................. 75,5
butadiene............................................... 73,0
styrene.................................................... 70,0
methylmethacrylate.............................. 57,5
izobutylene............................................. 53,0
-methylstyrene.................................... 34,5
Polymerization enthalpy at 25°C
∆Gmp < 0
Gmp = Hmp - TSmp
Ceiling temperature of polymn Tc – above no polymer formation
Gmp = Hmp - TcSmp = 0
Rate of polymn. = rate of depolymerization
!!!! All, chemical, kinetic and thermodynamic;conditions must be fulfilled !!!!
Monomers suitable for chain polyreactions:
- multiple bond between C atoms in molecule
- multiple bond between C and heteroatom in molecule
- (hetero)cyclic molecules
C C C CC C. . + -
radical polymerization ionic
A BA B+ -
Cationic polymerization
Anionic polymerization
+
-CH2 CH
D
+
-
CH2 CH
A
B
CH2CH2
+-O
CH2H O+
O-
Hmp Smp Gmp
1. < 0 < 0 < 0 at T < Tc
2. < 0 > 0 < 0 always not known
3. > 0 < 0 > 0 always
4. > 0 > 0 < 0 above Tf
Thermodynamical conditions of polymerizability
Monomer-H
(kJ mol-1)
-S
(J K-1 mol-1)
Ethene 93 155
Propene 84 116
But-1-ene 83,5 113
2-Methylpropene 48 121
Buta-1,3-diene 73 89
Isoprene 75 101
Styrene 73 104
-Methylstyrene 35 110
Vinylchloride 72 -
Vinylidenchloride 73 89
Tetrafluoroethene 163 112
Acrylic acid 67 -
Akrylonitrile 76,5 109
Maleinanhydride 59 -
Vinyl-acetate 88 110
Methyl-acrylate 78 -
Methyl-methacrylate 56 117
Enthalpy and entropy of polymn. for selected monomers at 25 °C *
* Brandrup J., Immergut E.H.
(Eds), Polymer Handbook, Wiley-
Interscience, New York 1989.
Sawada H., Thermodynamics of
Polymerization, Marcel Dekker
1976
Phase state
Monomer Polymer index for molar
termodynam. quantity
gas condensed (amorph.) gc
gas condensed (crystal.) gc´
Liquid condensed (amorph.) lc
Liquid condensed (crystal.) lc´
Liquid solution of polymer in monomer ls
solution m. solution of polymer ss
solution m. condensed sc
Means of polymerization
Monomer Tc (°C)
Styrene 310
Methylmethakrylate 220
α-Methylstyrene 61
Ceiling temperature Tc of selected monomers
dTc
Tc
dp
dT=
ΔH
TΔV=
ΔV
ΔHmp
dp
ln(Tc)p = ln(Tc)101,3 kPa + ΔV
ΔHmp
p
Dependence of Tc on pressure
Bond Energy between atoms capable of chain formation
Bond kJ/mol Bond kJ/mol
C – C
B – B
S – S
P – P
Se – Se
Te – Te
Si – Si
Sn – Sn
Sb – Sb
Bi – Bi
Ge - Ge
347,8
289,1
264,0
222,1
209,5
205,3
186,6
197,0
176,0
167,6
164,2
C – B
C – O
C – N
C – Al
C – S
C – Si
Al – O
B – O
Si – O
B – N
P - O
372,9
331,0
305,9
258,1
257,6
241,3
578,2
475,6
444,1
437,0
342,3
Capability to form isochain
PeriodeGroup
III. IV. V. VI.
2 ~5 B C N O
3 Al 45 Si 4 P 30 000 S
4Sc Ti Cr
Ga 6 Ge 5 As ? Se
5Y Zr Nb Mo
In 5 Sn 3 Sb ? Te
6La Hf Ta W
Tl Pb ? Bi Po