Class Note 1 [Compatibility Mode]

8/2/2019 Class Note 1 [Compatibility Mode]

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St ructure and Propert ies

of PolymersPolymer Physics I

Christopher Y. Li

Depart ment of Materials Science and EngineeringDrexel Universit y

ht t p:/ / w w w .mse.drexel .edu/ srg/


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The Future of PolymerScience

MATE 501: Structure and Properties of Polymers-CYL

Section 1


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http://people.ccmr.cornell.edu/~cober/NSFPolymerWorkshop/index.html


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1. Polymer Synthesis and New Polymeric

Materials2. Complex Polymer Systems3. Modeling and Theory

4. Characterization and Properties5. Processing and Assembly6. Technology and Societal Applications

Workshop Topics

http://people.ccmr.cornell.edu/~cober/NSFPolymerWorkshop/page13/page13.html


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Develop the synthetic, analytical, theoretical/computational, and processingcapabilities needed to master the structural control provided by new polymersand processes. In order to achieve unparalleled science and engineering

breakthroughs, we must bring separate research disciplines together. A commontheme in all breakout groups was the tremendous need for theory and simulationsperformed in synergistic collaboration with researchers in synthesis,characterization, and processing to provide guidance for these efforts.

Be able to tailor-make polymers. New synthetic methodswith exquisite control over molecular structure and functionpossessing a precision rivaling biomolecules must bedeveloped if we are to provide the materials needed for exciting

future advances. In particular, new materials including complex,hybrid polymers with specific properties made in smallquantities will be needed for the future applications envisagedby this workshop.

Recommendations:


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Develop real-time, high throughput, non-destructive, in-situ,multiscale polymercharacterization techniques. Multiple,

simultaneous analyses will provide real time information of unrivalledprecision to enable the implementation of precision processing and usherin the use of new self-assembling materials.

Be able to process polymers and complex hybrid materials with 2Dand 3D structural control down to dimensions of a few nanometersusing both directed and self-assembly. Processing combined with newsynthetic polymers that undergo self-assembly will permit materials withthe molecular precision needed in emerging technologies. Using directed

and self-assembly in combination provides unprecedented opportunitiesfor tailored materials that must be explored.

Recommendations:


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Accelerate research in technology-focused, enabling polymermaterials. A common theme in the breakout sessions was the vital andgrowing role that polymers will play in the energy, life science,

microelectronics, and information and communications technology fields.The use of polymers will increase dramatically in areas traditionallydominated by inorganic materials as a result of fundamental opportunitiesprovided by the coupling of polymer synthesis, processing,

characterization and theory.

Enhance cyberscience for the purpose of sharing modelingmodules within the broad polymer community, and encourage thecreation of digital libraries of extensive data on polymer systems.

Increasing amounts of information and new cyberscience tools arebeing produced, but there are few efficient means to access them in anorganized fashion. Research and teaching would be boosted by improvedaccessibility to these new tools.

Recommendations:


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Section 2

To catch up background



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Outline: A few topics in condensed

state polymersIntroduction, Polymer concept, history, commercialpolymers

Polymer Chain Structure, helical conformation idealchain, real chain

Crystalline and Liquid Crystalline Polymers (Structure)

Amorphous Polymerspolymer chain structure, polymer morphology, polymerstructure, amorphous state, crosslinked polymer andrubber elasticity, and polymer surface and interfaces.

Experimental technique: Light Scattering, X-rayscattering, X-ray and electron diffraction, polymermicroscopy.


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Textbooks and beyond

Introduction to Physical Polymer Science, by L. H.Sperling, John Wiley & Sons, Inc. 4th ed.

Polymer Physics, Michael Rubinstein and RalphColby, Oxford.

Macromolecular Physics, Vol. 1, 2, 3, BernhardWunderlich, Academic Press Inc. 1973.

The Physics of Polymers, Concepts forunderstanding their structures and behavior, G.Strobl, Springer.

Fundamentals of Polymer Science, by Paul C.

Painter and Michael M. Coleman. Principle of Polymer Chemistry, Paul Flory, Cornell

University Press, 1953. Principles of Polymer Systems 5th ed. Rodriguez,

Cohen, Ober, Archer, Taylor & Francis


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Journals Macromolecules Polymer Journal of Polymer Science Advances in Polymer Science Progress in Polymer Science Macromolecular Chemistry and Physics Journal of Applied Polymer Science

Science, Nature Journal of American Chemical Society Physical Review (Lett.; B, E, etc.) ACS Journals Wiley RSC


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As Early as Life Began: natural polymers - BIOMACROMOLECULESPolysaccharides: DNA, RNA, starch, cellulose, chitin, etc.

What are Polymers?

A-DNA Loop RNA

Hemoglobin

Chitin

Proteins and Polypeptides Natural rubbers

Silk

Cellulose


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As Broad as in Daily Life: synthetic polymers

polystyrene cis-polyisoprene poly(vinyl pyrrolidone)

polycarbonate poly(vinyl chloride)

What are Polymers?Polymers are very large molecules that are comprised or built up of smaller units or monomers.


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Focus of This Course SYNTHETIC POLYMER!!!

Definition of Synthetic Polymers: Poly+ Mer= many + parts or units Long-chain-like molecules or macromolecules consisting of

many repeating units (monomers) that are covalently linked,instead of physically-associated aggregates Molecular weight higher than ~10,000 g/mol (different from

oligomers, which is composed of a few repeating units)

Synthetic Polymers - Definition

Natural Polymers Synthetic Polymers

Repeating units many kinds one or a few kinds

Structure well-defined poorly defined

MW distribution 1.0 for proteins from 1.0 to ~30

Differences between Natural Polymers and Synthetic Polymers

See Sperling Table 1.8 for commercialization dates of important polymers


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Molecular Weight and Molecular Weight Distribution

Molecular Weight Distribution:

Average Mn

= NX

MX

/ NX

,

Average MW = NXMX2/ NXMX Average MZ = NXMX3/ NXMX2 Polymer dispersity index PDI = MW/Mn = 1 ~ 10 or even more

Molecular weight distribution is a unique characteristic of polymers.

Broad molecular weight distribution could broaden the crystal meltingpeak.

x = MX/M0X, degree of polymerization


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Nobel Laureates in Polymer Science- Chemistry

1963 KARL ZIEGLER and GIULIO NATTA for their discoveries in the field of thechemistry and technology of high polymers.

Ziegler Natta

1974 PAUL J. FLORY for his fundamental achievements, both theoretical andexperimental, in the physical chemistry of the macromolecules.

Flory

1953 HERMANN STAUDINGER for his discoveries in the field of macromolecularchemistry.

Staudinger


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Nobel Laureates in Polymer Science- Physics

1991 PIERRE-GILLES DE GENNES for discovering that methods developedfor studying order phenomena in simple systems can be generalized to morecomplex forms of matter, in particular to liquid crystals and polymers.

de Gennes

2000 ALAN J. HEEGER, ALAN G. MACDIARMID, and HIDEKI SHIRAKAWAfor the discovery and development of conductive polymers.

Heeger MacDiarmid Shirakawa


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The Nobel Prize in Chemistry 2005

"for the development of the metathesis methodin organic synthesis"

Yves Chau vi n Rober t H .

Grubbs

Richar d R.

Schrock

Institut Franaisdu PtroleRueil-Malmaison,France

CaliforniaInstitute ofTechnology(Caltech)Pasadena, CA,USA

MassachusettsInstitute ofTechnology (MIT)Cambridge, MA,USA

b. 1930 b. 1942 b. 1945


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the Charles Stark Draper Prize2002: Robert Langer

for the bioengineering of revolutionary medical drug delivery systems.


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Polymer Science and Engineering- A

Multidisciplinary Field

Chemistry Physics

Biology Engineering

MaterialsScience

POLYMER


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Step Growth vs. Chain Polymerization

Which is step growth? Which is chain polymerization?

step growth

chain polymerization

chain polymerization


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Step growth



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Chain Polymerization

Four Steps:Initiation, propagation, (chain transfer), Termination

Initiation

propagation


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Chain Polymerization: Termination

Combination

Disproportionation


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Chain Transfer


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History of Macromolecules and Polymers

1846Christian Schnbeininvented gun cotton

1862Alexander Parkes made

articles from plasticized cellulose nitrate

1870John and Isaiah Hyatt patented celluloid

1892Charles Cross, Edward

Bevan, and Clayton Beadlepatented regenerated cellulose,

i.e., viscose rayon fibers andcellophane films


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1977Alan Heeger, Alan

MacDiarmid, and HidekiShirakawa discovered and

developed conducting polymers


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The power of MW


See Sperling Table 1.4 and 1.6 for common polymers.


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Solid Intermediate Liquid

Crystal

Mesophase

GlassMesophase Melt

GlassDisorder

Increasingorder

Immobile Increasingly mobile

Td

Tm

Ti

T

g

Tg

Possible phase t ransit ions in onecomponent system


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Polymer Chain Structure


The conformation of the chains in space. The term conformation refersto the different arrangements of atoms and substituents of the polymerchain brought about by rotations about single bonds. Examples ofdifferent polymer conformations include the fully extended planar

zigzag, helical, folded chain, and random coils.

The molecular weight and molecular weight distribution of themolecules.

The configuration of the chain. The term configuration refers to theorganization of the atoms along the chain. Some authors prefer the

term microstructure rather than configuration. Configurationalisomerism involves the different arrangements of the atoms andsubstituents in a chain, which can be interconverted only by thebreakage and reformation of primary chemical bonds.


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isomerism


Sequence Isomerism

Stereoisomerism

Optical Isomerism

Geometric Isomerism

Substitutional Isomerism

Head to Head and Head to


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Head-to-Head and Head-t o-

Tail Conf igurat ions


head-to-tail

head-to-head

STEREOCHEMI STRY OF


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STEREOCHEMI STRY OF

REPEATI NG UNI TS


Chiral Centers

Such carbon atoms are referred to as pseudochiral centers in long-chainpolymers because the polymers do not in fact exhibit optical activity


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Tact icit y in Polymers


Three different configurations of a

monosubstituted polyethylene

Meso and Racemic


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Meso- and Racemic

Placements


The Fisher projection in equation(2.10) shows that the placement

of the groups corresponds to ameso- (same) or m placement ofa pair of consecutivepseudochiral centers. Thesyndiotactic structure in equation

(2.11) corresponds to a racemic(opposite) or r placement of thecorresponding pair ofpseudochiral centers. It must beemphasized that the m or r

notation refers totheconfiguration of one

pseudochiral center relative toits neighbor.

REPEATI NG UNI T


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REPEATI NG UNI T

I SOMERI SM


Optical Isomerism

Geometric Isomerism

Substitutional Isomerism


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-A-B-A-B-A-B-A-B-A-B-A-B-A-

-A-A-A-A-B-B-B-B-B-B-A-A-A-A-

-B-B-B-B-B-B-B-B-B-B-B-B-B-B-B-

A-A-

A-

A-

A-

A-

A-

A-

A-

A-

A-

A-

A-

A-

A-

A-

A-

A-

A-A-

Poly-A-block-poly B

Poly-B-graft-poly A

Alternating copolymers

-A-B-B-B-B-A-A-B-B-A-B-A-A-B-B-

Random copolymers

Homopolymer vs. Copolymer


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Six basic modes of linking two or morel id tifi d ( ) A l


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polymers are identified . (a) A polymerblend, constituted by a mixture or mutualsolution of two or more polymers, notchemically bonded together. (b) A graftcopolymer, constituted by a backbone ofpolymer I with covalentlybonded sidechains of polymer II. (c) A blockcopolymer, constituted by linking two

polymersend on end by covalent bonds.(d ) A semi-interpenetrating polymernetwork constituted by anentangledcombination of two polymers, one of whichis cross-linked, that are not bonded toeach other. (e) An interpenetrating

polymer network, abbreviated IPN, is anentangled combinationof two cross-linkedpolymers that are not bonded to eachother. (f ) AB-cross-linkedcopolymer,constituted by having the polymer II

species linked, at both ends, onto polymerI. The ends may be grafted to differentchains or the same chain. The totalproduct is a network composed of twodifferent polymers.

Important Concepts


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Important Concepts

Important Concepts


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Important Concepts

Polymer Architectures


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Polymer Architectures

Contour length, Rmax


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Contour length, Rmax

Polyethylene, witha given MW, what is

the contour length

TransGauche


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Conformations



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Butane CH3-CH2-CH2-CH3potentials

)(mole

kcal

Polyethylene potentials


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Rotational isomeric state model


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Rotational isomeric state model

Random coil conformation

A number of differentconformations

320,000

Random conformation of al l h i


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macromolecular chain

Random flight

There is not only totally free rotation around the bonds of the chain, but the chainis freely joint (the valency bond angle is no longer fixed but can take any value)

The chain can pass through regions of space that are already occupied by other

bits of itself.

Free Joint Chain:

Three-Dimensional Random Flight


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Three Dimensional Random Flight

i

N

i

lR

1

1/2 Root mean square end-to-end distance

Polymer conformation


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Polymer conformation

A polymer chain can take on an enormous range of

configurations as a result of bond rotations.

These configurations or conformations can be described

statistically, with the end-to-end distance R being a useful

parameter for doing this.

The average value of R taken over all possible conformations

can be expressed in terms of its root mean square value

1/2, which is proportional to the square root of the number of

bonds, N1/2.

The distribution function P(R) takes the form of a Gaussiancurve, to a first approximation.

From Free-Joint to Free Rotate


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o ee Jo t to ee otate

_______

_______

cos1

cos1

cos1

cos1

= Nl2

=l2

2)cos1(

)cos1(cos2

cos1

cos1

N

N

= Nl2

cos1

cos1

Considering restricted (hindered) rotation:

Free rotation:

2

0

2NlCR

Equivalent freely jointed chain


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Equivalent freely jointed chain

The equivalent chain has the same mean-square end-to-end distance and the same maximum end-to-end

distance, but has N freely jointed effective bonds of lengthb. b is called Kuhn length

Nb = Rmax = Nb2 =b Rmax =C nl2

N = R2max/ C nl2

b = /Rmax

= C

nl2/R

max

For PE, b = C l2

n/nl cos(/2) = C l/cos(/2)

= C

nl2

Colby and Rubenstein

Chain characteristics of commonpolymers


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polymers

Colby and Rubenstein



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Polytet rafluoroethylene rotat ional potent ials


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Polytet rafluoroethylene rotat ional potent ials

s tableposit ion

gauche (+ )posit ion

gauche( - )posit ion

stableposit ion

~ + 15 ~ -15

Rotation by +15 gives

a right-handed helix

Rotation by 15 yields

a left-handed helix

Helical conformat ions of Class 1Macromolecules


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Macromolecules

Polyethylene CH2-

Polytetrafluoroethylene CF2-

21helix

137helix

Wunderlich

Conformat ion helices


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Conformat ion helices

Identify period

c along z

131Perspective drawing and

projection along z

Aut:Rotation necessary to go from lattice pointto lattice point:

Translation necessary to go from lattice point

to lattice point:

u/2 u/c

t: turns to the next identical helix point

u: periodicity (# of helical lattice points

per identical period)

c: distance to the next identical helix

point

Projections

of varioushelices

21 31 41

61525142= 21

62= 31 71 72 73

92918381

32 31

Wunderlich

Secondary Structures of Proteins


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helix pleated sheets

Secondary Structures of Proteins


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The three-fold helix of isotactic polypropylene in front ofthe Giulio Natta Research Center in Ferrara, ItalyPhoto courtesy of Pr. Galli QuickTime?etun

dompresseurGraphiquesontrequis pourvisionner cette image.

Institut Charles Sadron Strasbourg

Helical conformat ions of Class 2

Macromolecules


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Macromolecules

Rotational Potential

Energy

231helix

Polyoxymethylene

Polypropylene (isotactic)

planar zig-zag

view along the planar zig-zag:

d-RH-helix1 120, 2 0

d-LH-helix

1 0, 2 240(-120)

2 95helix102 rotation for each angle from the

shown all-trans conformation

CH2 O

CH2 CH

CH3

Wunderlich

Openness of helices


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p

The side group is marked and is takenas the helix lattice point. The morecrowded the backbone chain becomes

due to a large side group close in, the

more does the helix open up. 1and2decrease by about 20 in going from231to 241

Perspective Drawing of

Isotactic Vinyl Polymer Helices

231 272 241

Wunderlich

Dense packing of rods


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p g

Packing fraction

Coordination Number CN = 6Compare:

Close pack of sphere CN 12,

K = 0.741;

Packing of rods with CN 4,K = 0.785

907.0 areatotal

circlesofareaK

Wunderlich

Packing of Helices w it hLarge Side groups


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Large Side groups

CN = 4

K = 0.785 when touchingK = 0.92 with interpenetrating

helices of 59% thread depthRH screw intermeshing with LH screw

Wunderlich

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Class Note 1 [Compatibility Mode]