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Introduction to MacromoleculesIntroduction to MacromoleculesCHM5080 (CUHK)CHM5080 (CUHK)CHEM588/324 (HKUST)CHEM588/324 (HKUST)CHEM6108 (HKU)CHEM6108 (HKU)
Lecturers: Chi WU (CUHK), E-mail: [email protected]
Ben Zhong TANG (HKUST), E-mail: [email protected]
Wai Kin CHAN (HKU), E-mail: [email protected]
Time/date: CUHK: L2 Science Centre Feb 18 &March 4;(10:30am-12:30pm, 2:00-4:00 pm)
HKUST: Rm 2306 (near lifts 17/18) March 18 &April 1;(10:00am-12:30pm, 2:00-5:00 pm)
HKU: Lecture Theatre P1 April 8 &April 22 ;LG1 Chemistry Building (10:30am-12:30pm, 2:00-4:00 pm)
Final Exam: CUHK/HKUST/HKU May 6(Saturday)
Textbooks:
Introduction to Polymers, 2nd edition
Introduction to Macromolecular ScienceBy Petr Munk, 1989, John Wiley & Sons, QD381.M85
y . . oung an . . ove , , apman a , .
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OutlinesCUHK
.2. Structures of macromolecules
.
HKUST4. Classification of polymerization reactions5. Step (or condensation) polymerization
. a n or a on po ymer za on7. Copolymerization
HKU
8. Ionic polymerization
9. Coordination polymerization10. Controlled radical polymerization
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Detailed Outline-HKU
8. Ionic polymerizationAnionic polymerizations
Initiators, Choice of monomers, Synthesis of block
copolymers at on c o ymer zat on
Initiators, Monomers, Reaction mechanism and molecular
Ring opening polymerizations involving ionic intermediate
. oor na on po ymer za on
Ziegler-Natta Catalysts for the polymerization of olefins
properties
Other initiators for coordination ol merizations e. .
2005/2006 Macromolecules
metallocene catalysts)
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Detailed Outline-HKU Cont
10. Controlled radical polymerization
Overview of polymerization mechanism and kinetics
Nitroxide mediated polymerization (NMP)
Radical addition fragmentation Transfer (RAFT)
A lications of CRP in the s nthesis of functional block
copolymers
.Conjugated polymer
Ring Opening Metathesis Polymerizations
A lications of these ol mers
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The Basics of Macromolecules
Natural Macromolecules Synthetic Macromolecules
Proteins, DNA, RNA
Polysaccharides cellulose: lants & animals
Polystyrene, polyethylene
Poly(vinyl chloride) Pol esters ol urethane ...
Sma mo ecu es
Macromo ecu es
The difference between small molecules and macromolecules
*Homogeneous
* No swellin in dissolution
* Inhomogeneous (size & mass)
* Swellin in dissolution* Purification methods
* Low viscosity
* Precipitation, GPC,
* High viscosity
2005/2006 Macromolecules
mp e s ruc ures omp ca e s ruc ures.
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Structures of macromolecules
*
Configuration:how they are connectedHomopolymer & heteropolymers:
block, seqential, graft, random, ... linear, branching, star, grafting, ladder, ...
* Secondary structures Comformation: folding, helix, sheet, ...
* Special arrangementsof larger segments(helix & sheet) to form a complicate structure
* Quaternary structures Spatial multi-chain aggregates, intra- andinter-chain interaction, e.g., triplethelix and enzyme
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* Backbone contains only carbon atoms
- Polymeric hydrocarbons: PolyethylenePolypropylene isotactic, syndiotactic & atactic
Pol butadiene 1,2 addition and 1,4 addition cis & trans)
Low (H.P.) and high (L.P.) density PE
tures
Polyisoprene -(CH2C(CH3)=CHCH2)n-natural rubber
Polystyrene The most representative polymer
struc - Halogen-containing: Poly(vinyl chloride)
Polytetrafluoroethylene
-(CH2CCl)n- common polymer
Teflon, The king of plastic
Polytrifluorochloroethylene Tou h and inert
rima - With polar side groups: Poly(methyl methacrylate) Organic glass
Poly(hydroxyethyl methacrylate) Gel contains 35% water
Polyacrylamide Typical water soluble polymer
Polyacrylic acid Washing power, useful polymers
Pol vin l alcohol Pol vin l rrolidone .
- Polymers with heteroatoms in the backbone:
Polyether - PEO; Polyesters -(O-(CH ) -CO) -, PCL; Polycarbonates -(O-R-O-CO) -;
2005/2006 Macromolecules
Polyamides -(NH-(CH2)a-CO)n-;Polyurethanes -(NH-R1-NH-CO-O-R2-O)n-;Polyureas; ...
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Structures of macromolecules
*
Configuration:how they are connectedHomopolymer & heteropolymers:
block, seqential, graft, random, ... linear, branching, star, grafting, laddle, ...
* Secondary structures Conformation: folding, helix, sheet, ...
* Special arrangementsof larger segmentsto form a complicate structure, e.g., helix
* Quaternary structures Spatial multi-chain aggregates, intra- andinter-chain interaction, e.g., triplethelix and enzyme
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Structure of a protein chain: Primary: Secondary and Tertiary Structures
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*. Helical structure - Proteins am lose and nucleic acids
tion
Energy vs Entropy Random coil vs Ordered conformation
It re uires two h dro en bonds in the ormation o the helix not roline .
forma
It contains 3.6 amino acid residues per turn; subsequent residues are
rotated 100o
with a pitch of 5.4 A; and the translation is 1.5 A per residue.
s-Co *. Chain folding of some regulated heteropolymer chains
Stickers moverandomly like a
uctur
gas
Stickers move ina more correlatedfashion like a
liquid Stickers are
a
ryst
heat heat
res r c elike a
solid
Secon
Collapsedcore-shell
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Random coil
nanoparticle
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T < ~32 oCA single polymer chain
Tincreases
core-s e nanos ruc ure
dcreases
PNIPAM-g-PEO
, , ,
79, 620 (1998);Macromolecules, 30, 7921
1.8 80yrene: an imitated drug
Applications
1.4
1.6
40
60
1/I3
T
/o
ne o e env s one
applications is the smart
temperature-sensitive1.2
20
I C
. 010 20 30 40 50
t / min
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Protein denaturation Heat denatured & chemical denatured
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Structures of macromolecules
*
Configuration:how they are connectedHomopolymer & heteropolymers:
block, seqential, graft, random, ... linear, branching, star, grafting, laddle, ...
* Secondary structures Conformation: folding, helix, sheet, ...
* Special arrangements of larger segmentsto form a complicate structure, e.g., helix
* Quaternary structures Spatial multi-chain aggregates, intra- andinter-chain interaction, e.g., triplethelix and enzyme
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eat
Secondar structure - helix
em ca
Particular spatial arrangement
Specific & fast Energy - adenosine triphosphate (ATP)
Chymotrypsin - a hydrophobic pocket - aromatic amino acids
Tr sin - an ioni ed carbox l - interacted with the basic rou s
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2005/2006 Macromolecules
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A zig-zag chain A thread chain A random coil
Let us start with a polymer chain in one dimensional space.
It hasN e ments and each se ment has a len th o b.o
b-b
After N steps and ifn steps are positive, R = bn + (-b)(N-n) = b(2n-N)2/Nn
NIf
The chance (probability) to findnpositive steps is a binomial
distribution because Pn is related to (p + q)Nwhen p = q = 1/2. !)(!
!
nNn
NP
N
n
=2
1
NN
nNn N! +The mean value ofncan be calculated as
22
2
1
1
1
2
1
2
1 1 NNnNn
NN
nNn
nNnPn
NN NNNNN
n =
=
=
=
= !! !)(!! !n
qp
nNn
qp
!)(!
+=0
= 0=
4
1
11
1
2
1
2
1
1 10
2
0
22 )(
!)(!)(
!
!)(!)(
!)(
!)(!
! +=
=
=
= =NN
nNn
N
nNn
Nn
nNn
NnPnn
N
n
N
n
NN
n
NN
n
n
4
2 Nn =
N
Step motion: Rn = b or -b nmmn bRR 2= 21
2
11
2NbRRRR
N
n
n
N
m
m
N
n
n = =11
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( ) 20
222)]2([ NbPNnbRRR
n
n=
===22 NbR =bNRRRMS
222 =
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N
!)(! nNn2
Pn = ?,
=nP
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In a good solvent, a chain is in the random coil state.
Radius of gyrationHydrodynamicRadius (Rh)
End-to-End
Distant
R = rN - ro
R 121
21 N /rr 212005/2006 Macromolecules
.hR 0
NR
i
iRMS =
=
=r
6
= bRg
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Radius of gyration (Rg) i i+1i+2
=
= Ni
i
N
i
ii mm11
/rrGrr
The gravity center:
1
Nri
r1rN
0
NmmRN
i
i
N
i
i
N
i
iig /)rr(/)rr( GG2
11
2
1
2 rrrr = 234
5
Thin rod: Rg2 = L2/12
S here: R 2 = 3/5 R2= ===
N
N
i
ii
N
N
i
jii
N
j
N
i
ii mmm
R 1
2
1
22
12
)rr()]rr()rr[()rr( GGGrrrrrrrr
Thin disk: Rg2 = (1/2)R2=i ii ii immm
111
22
For an idea chain ( ) jibjiij 222 rrR rrr2 NN NN
bNRRRMS21
212 /
/ =
)(
)(
16
2
22
211 112 ++==
==
==N
NNb
NNm
m
R ii j
N
i
i
i
g
4526 .RSM
R
R
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=
( ) 66,2
12 bN
bRRNAs gg ===
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bDimensions of chains with short-range interaction
The end-to-end distance: =
= Ni
i
1
bRrr
i-1 i
ri+1 b( ) 212 /NbRFJ =
( ) 2122111
21
1
1//
/
cos
cosbbRRR
+=
= bb
N
J
J
N
i
iFR NbR rrrrr
cos1
cos1
+
=b
b
FJ
FR
R
R
If the rotation is restricted,
2121
2
1
1
1
1//
cos
cos
+
+=
b
bRR NbR
b ~ 70 043.1
FJ
FR
R
R
In the state 7.0= FRR
R) 21276 NbR . )(6.27.6 PER
R
FJ
Statistical coil chain ( ) 212''bNRS = where b = mb, N = N/m and Nb = Nb = LSome defined parameters
M
RA =
2
2
2
2
Nb
R
R
RC
FJ
== 1
2=
b
LC
P
PP: 6 PEO: 4 PE: 7
LP: is the length
of persistence.
2005/2006 Macromolecules
For linear chains:
5.053=
MNR PS: 10; PMMA: atactic: 7;
syndiotatic: ~7; isotatic: 4.
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Worm-like polymer chain
cos1
cos1cos...coscos
12
=++++=
NN
bbbbbXx
dLd =rr
===
=
= cos1cos
1
11
1
bb
bL
i
i
i
iP rr ( ) ( )[ ]
===P
P
N
P
N
PL
LLLLX exp1)cos1(exp1cos1
The rigidity of a worm-like polymer chain depends on its chemical structure, the short and
long range interactions between chain segments, and ... e.g., PPTA and polyelectrolytes ...
2/1
=
=
PPLP
P
LL
Pe
L
LLLdLeLR 11212
0
2
dLXrd 22 = 2 311
2
+
+=
P
L
P
P
PG
L
Le
L
L
L
LLR P
For flexible chains 0/ >> PLL
PeLLQ LLLLLR PPP 222
22 =63
...1
3
R
L
RPPP
G=
+=
Short ran e 1) IR: vibration and rotation; 2) NMR: chemical shift;
Experimental Methods
Configuration 3) chemical analysis, GC, UV and MS; and .
1) viscometry: ~ Vhor Rh; 2) laser light scattering: Rg
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Conformation
n h ; uorescence: ; x-ray an neu ron sca er ng
& diffraction; 5) relaxation: mechanical, electrial, optical, ...
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Structures of macromolecules
*
Configuration:how they are connectedHomopolymer & heteropolymers:
block, seqential, graft, random, ... linear, branching, star, grafting, laddle, ...
* Secondary structures Conformation: folding, helix, sheet, ...
* Special arrangementsof larger segmentsto form a complicate structure, e.g., helix
* Quaternary structures Spatial multi-chain aggregates, intra- andinter-chain interaction, e.g., triplethelix & enzyme
2005/2006 Macromolecules
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Small molecules Conventional colloidsassembly Physical methods
Chemical methods
Macromolecules Polymeric colloids (supramolecules)assembly
Poly(phenyl vinyl
sulfoxide)(PVSO)Polyacetylene (PA)Poly(p-methyl styrene)
n PhSOH
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SelSel --assembl o rodassembl o rod--coil diblockcoil diblock
copolymers in dilute solutioncopolymers in dilute solution
Assembled
Rc
RR
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Molar mass distributons Mn ,Mw ,Mz, M, ... fn(M); fw(M); fz(M)
Absolute methodsT e end-group, co igative properties
MS, light scattering, ultracentrifuge.
Relative methods viscosity, chromatography, FFF
f M Mf M w n( ) ( ) f Mf M M f M z w n=( ) ( )2 f MM
f Mwn
n ( )iii nMW =2
iiiii nMnWZ ==
The n-average molar mass M Mf M dM
f M dM n
no
no
=
( )
( )
M
M N
Nn
ii
i
ii
= =
=
1
1
The w-average molar mass M M f M dM
Mf M dM
Mf M dM
f M dM w
no
n
wo
w
= =
2 ( )
( )
( )
( )M
M W
W
M N
M Nw
ii
i
i
ii
i
i i
= =
=
1
2
1 = =The z-average molar mass M
M f M dM M f M dM
z
wo
no= =
2 3( ) ( )
M
M W M N
z
i
i
i i
i
i
= =
=
2
1
3
1
Mf M dM M f M dM wo
no( ) ( ) M W M N i ii i ii= 1 21
Schulz-Zimm Distribution+
Poisson Distribution Logarithmic normal distribution
2005/2006 Macromolecules
f M
z
M ew z bM ( )
( )
=++
1f M
M
w
( ) ( ) exp[( )
]/= 22
1 2
2
f M A
z
nM
Pw
M
( ) exp[ ( ( )] 1 l
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Review MacromoleculesNatural: DNA, protein,Polysaccharides...
Synthetic: i erent po ymers ...
Difference between small and macro-moleculesHigh-order structures
The statistic nature of chain conformations
R = 1/2 = N1/2b
Rg = 1/2 = (N/6)1/2b
Rh
~ Rhard
with the same D
- - -
31~Different scaling relationships between the
size and mass of linear flexible coiled chains
53g
[ ] 41 withM~
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Experimental Methods
For polymer chains,molar mass distribution, conformation
chain size distribution are im ortant because M and R
are directly related to properties and performance.
Absolute methodsfor low molar mass chains :
end-group; vapor pressure osmometry; NMR;
which does not require at
least two or more narrowly
distributed standards with
co ga ve proper es; an - -
for high molar mass chains :
known molar masses
and static laser light scattering,
Relative methodsfractionation; translational diffusion;
viscocity; chromatographic methods;
2005/2006 Macromolecules
which requires ca ibration dynamic laser light scattering; and
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In solutionthermodynamics
hydrodynamics
In bulk (solid) amorphouscrystalline-
In solution:In solution: dissolution process G G n G mix i
N
i o
G
n i=
*The Flory-Huggins TheorySimple & Effective: ~1940s developed
G = H - TS when T = constant
G H T S mix mix mix )( pspsmix VH = solubility equationCondition : no volume change in the mixing
i iF=
= e1/2and e is the cohesive energy density,i.e., the vaporization energy of unit volume
F is the attraction
force per molar
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m liquid under zero pressure.chemical groups.
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The end-group analysis Mn < 10,000 g/mol
e.g., Nylon-6 H2N(CH2)5CO-(-NH(CH2)5CO-)n-NH(CH2)5COOH
We can titrate the number of ends H2N- and -COOH
For a monodisperse sample : M = W/n ;
For a polydispersed sample, W = niMi; n = ni, andMn = W/n
Colligative properties
The boiling or freezing point change
limC
b or f
v or f n
T
C
RT
H M=
0
2 1
why Mn ?
Membrane osmometry popo+
/C = RTMfor small molecules
solution solvent
/C = RT/Mfor macromolecules
CRT
MA C A C + + +( )1 2 3 2 L
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MALDI-TOF-MS and NMR
Here we only ontline their basic principles.
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Laser light scattering (LLS)
E = Eosin(2 vt - )Es = k (d
2P/dt2) = E = 4 P = p + H = ocE i = = oc
i
r
c E
r
Io
o o
o
o< > =16 164 2
4 2
2
4 2
4 2
' '
( )i ~ -4 i ~ r --2
i ~ 2 ~ V2For N particles
I = Ni
Rayleigh ratio : Rvv(q) =Ir2/Io = KCM K
ndn
dC
N
o
AV o
= 42 2 2
4
( )Rvv(q) =KCMw
For a large particle : Rqr
r
i jNN= 16 44 2
sin( ), KCA C+1 2 2
j
o vv w
qn
o
= 42
sin p q
R q q
R q
q Rvv
vv
g( )( )
( )
= == < > +0
11
3
2 2L
i KCR M
q R A C g Z( )+ < > +1 1 13 22 2 2
2005/2006 Macromoleculeswhy Z ? The z-average ?
400 pin holeCuvette
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Focus Lens400 pin-hole
Position-sensitive
Spectra-Physics Helium Neon Laser632.8 nm WavelengthLaser
Monitor diode
o e aser umpe : aser532nm Wavelength
Cell housing and
Laser
Encoder Stepping motor
index matching vat
Photon
Static, Classic LLS(time average intensity)Rotating Arm
CounterDynamic, Modern LLS(digital time correlator)
Polymer : 5x103 - 107 g/mol
Particles : 2 - 2000 nm
Photomultiplier tube
Preamplifier/DiscriminatorDilute solution / suspension
C = 10-3 - 10-6 g/ml
2005/2006 MacromoleculesLaser Light Scattering Spectrometer incorporated with differential refractometer
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Static LLS Angular and Concentration dependence of
CAqRKC g
22
211 + SII
MqR WVV 3)(+
222
)/(4 dCdnn= 4n=
)()()(
oo
rro
VVVV
n
n
I
IIqRqR =
4oAN o r
A plot ofR q
vs C AVV
q"[
( )] "
0 2
A plot ofKC
R qvs q R
VV
C g"[( )
] "
02 2
2
TheextroplationofKC
R qM
VV
C q W[( )
] ., 0 0
z1/21/Mw
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Dynamic laser light scattering
* Intensity fluctuation :
I
slow fastDynamic LLS
I
t
The ast the movements,
the fast the fluctuation
* Doppler frequency shift :
+
0 0+0 ~ 1015Hz ; 10 510 7HzIt is rather difficult to detect . 202 )(
)( =
S
- 0 0+0
* Time correlation function: deSEE i )()()0( * deEES i= )()0(1)( * deGg )()(0)E(E)( *)1( 1=
),q()0,q(),q(
|)2( IIG =The Siegert relation
2005/2006 Macromolecules
)0(0)E(E 0
c]|),q(|1[)0,q( gI
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A typical time correlation function of the chains in solution
0.8012.00
0.604.00
8.00
G
(
)
0.40A]/A 0.00
-2
10-1
10 -1
2)
(t,q)
)1)(1( 222 qRfCkDq gd +0.20
[g Dq
Cq
=
00
2
0.0 20.0 40.0 60.0 80.0 100.00.00
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Size exclusion chromatorgraphy
V = V0 + Vifor small M : Ve = V0 + Vifor large M : Ve = V0
In general : Ve = V0 + ViV = A + B lo M V = A + B lo M standards e
In practice , one can obtain Veand calculate []M . If knowing [], one can findM.Detectors
* differential refractometer ; * viscometer ;
* UV ; and * small angle light scattering from Veto M
Field flow fractionation (FFF)wflow Tk
D
fuF
B
=
=
x = 0 exp -x w ere = u =
If d > l > 2 m, it will be a steric FFF - Larger ones come out first.
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Viscoelastic Properties of Bulk Polymers Temperature
Small molecules (liquid) Crystals and glass
viscoelastic
Macromolecules (melts) Crystalline and amorphous
Stress : F/A = Shear stress
F
Strain : L/L = = L
L = = E E : the Youngs modulus Elasticity
The tensile strength : The elongation at break F
= omp ance
E = 2G (1 + )
Viscosity () LL
d =
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= -( / ) / ( L/ )
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The Maxwell Model The stress relaxation T = constantElastic
viselT + el = G vis = (d/dt)sinceViscous0
11=+=+=
dt
d
Gdtdtdt
dviselT
)exp(0
t=
where
=
CBBC +For a dynamic experiment
CBBC)sin()cos(assuming&)sin(If 0 tCtBtT +==
coss ncos0GG
22 G ("
0= GanG
++ )sin()1()cos()1()( 22220 ttt
G G
=m00 1)("G
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Storage modulus Loss modulus )(' =G
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The Voigt Model The creep experiment T = constant
viselT + el = G vis = (d/dt)since
dt
dGT
+
)exp(1)(
tG
t Twhere
=
astic
co
us
E Vi
+ CGB +0For a dynamic experiment )sin()cos(assuming&)cos(If
0tCtBt
T +==
0 BGC 0
=G )(" ++ )sin()1()cos()1()( 22220 ttt
G G
=00
=)("G2005/2006 Macromolecules
Storage modulus Loss modulus
=)('G
E l Polycarbonate with
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Example Polycarbonate with
two molar masses.
The time domain can be divided intofour regions, I, II, III and IV.
I: t
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logGThe Time-Temperature Equivalency
log a1
G(t, T) = G(t, T) G(t2, T1) = G(t1, T2)
G(t3, T1) = G(t2, T2)The Williams-Landel-
log a2
4, 1 = 2, 3
log t1 + log a = log t2
Ferry (WLF) equation
)(1 oTTC
aog
l log t1 log t3log t2 log t4
2 o t1 = t2 a
logGIf Tg is taken as T0 , VSP
The glass transition temperature (Tg)
log t2 - log a1log t3 - log a1
11
2
C
TT
C
C
aog
TT gg l
T
a
log t3 - log a2
The universal
values of C1and C2
C1 = 17.4
Tg,2
,
ec
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log t1 log t2
4 - 2C2 = 51.6 T
g, true
T > T Plastic materials
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The Glass Trenasition Temperature (Tg)Tg > Troom Plastic materials
or < T nd T , , , ,
3. The chain length Tg
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4. The cross in ing o the chains. . e m x ng o erent po ymers.
m
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The Avrami equation )exp(1m
Kt
Crystallization is the crystallized fraction and can be determined by any property,such as volume, diffraction intensity, . M depends on geometry,crystallization rate, & nucleation mode so that m is in the range 0.5-4.
P
PcP = Pa + (Pc - Pa) 0VVt =e.g.,
0 1Pa
0
In practice, plot ln [ ln [1/(1- )] ] versus ln t The glassy polymers
Non-equilibrium
The specific volume depends on how fast a sample was cooled
down and how long it remains at a particular temperature.
= 0 + free 0 : t e core an v rat on free : t e trans at onVfree ~ 2.5%V
S 22 vkB 1Tvke e as c ne wor sPTL ,
2 + 20 L1
TvkF
B dLTvk 2 2RT RT3 RT
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2
VA LV
+2 2
+CM C
M
CM
H
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The Crystalline Polymers fm
HT
=STHG f
Folding chains and Spherulites G is continuous at Tm, but not S or V.
G = H - ST; H = U + PV; U = Q - PdV;
Q = TdS dG = VdP - SdTS
T
G
P
V
P
G
T
=
dTT
dPP
dGPT
+
=
T
eT?
T
eT
,
T < Tg; Tg < T < Tm ; andT > Tm
Tg is related to the cooling rate, but not Tm.
In reality, the process of Crystal < > Melts is a kinetic process. For example,
Tmdecreases with Tcr; Tm is higher than Tcr, the crytal size decreases as thecooling rate increases; and Tm < Te (infinite size), .
Amorphous - it can be viewed as a supercooled liquid
2005/2006 Macromolecules
assy s a eCrystalline (0-100%) - it can be viewed as crosslinking points
M h l f lli l
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Morphology of crystalline polymers
The chain folding: 10-20 nm thicknessSpherulites in a concentrated solution.
Mechanical properties ofcrystalline polymers Drawn in fibers
0.5 < Tg/Tm < 0.8 Below Tg => Glassy and above Tm => Melts
If Tg < T < Tm,the crystalline regions act as crosslinking points, so that the
2005/2006 Macromolecules
mater a s w e ar an toug . uc a structure can a so e ac eve y
copolymering some hard segments into flexible chain backbone.
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Multicomponent and multiphase materials
Plasticization of polymers
nt sma mo ecu es to ecrease g.
Heterophase polymers
Blending of different polymers
Block and other structure copolymers
To obtain different Tg
and toughness.
2221 VnVnV
G mixmixV
mix +==
222,12
2
21
1
1 lnln BVV
RTGVmix + +
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1
2,1
2,1V
B=where
MD2 MD3 MD4
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MD2 MD3 MD4
A ol mer el is a three-
dimensional networkswollen by a large amount
MD5 MD6 MD7p = . of solvent. It has some
properties betweensolutions and solids.
SEM micro ra h of H-
MD2 MD3 MD4
sensitive copolymer
P(DEAM-co-MAA)MD5 MD6 MD7
pH = 9.5
hydrogels obtained at
different pH values.
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25 oC 37 oC
mixingswelling state shrinking state
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