1-3 What is the degree of polymerization of each of the following?
N
OCH2CH2 OC
CH2
CH2OH O O
HO OH
C Cl
Cl (a)
(b)
(c)
(d)
C
C
with molecular weight 100,000
with molecular weight 100,000
with molecular weight 100,000
with molecular weight 100,000
O (CH2)5 H
m
n
x
O O
1-4 (a) What is the functionality of the following monomers in reactions with styrene?
H C CH2?
(i) CH2 C H
CN (iii)
(iv)
CH3 CH2
C O C H
H H C CH2 O
CH2OH
(ii) H2C C H
CH2OH
C O C H
H H C CH2 O
(b) What are their functionalities in reactions with divinyl benzene (1-15)?
55 Problems
1-5 Draw structural formulas (one repeating unit) for each of the following polymers:
(a) poly(styrene-co-methyl methacrylate) (b) polypropylene
(c) poly(hexamethylene adipamide) (d) polyformaldehyde
(e) poly(ethylene terephthalate) 1-6 Name the following:
(a) (b)
(c)
CH2
OCH2CH2CH2CH2 OC
CH2 C Cl H C
C O
x x
x
CH3
CH3
(d) (e)
(g)
(i) CH2 C x
CH3
C OCH2CH3
(f)
(h)
(j)
CH2 C x H
C O
CH2 C
Br H
x
OCH3
CH2 C x H
O C CH3
CH2
5 x
C O
N H
C
CH3
CH2CH2
O
C O O
N O
N H H
O
O
CH3
CH3 O i
x
1-7 Which of the following materials is most suitable for the manufacture of thermoplastic pipe? Briefly tell why.
(a) CH3 ( CH2 )
29 CH3 (b) CH3 ( CH2 )
14,000 CH3 (c) CH3 ( CH2 )
200,000CH3
1-8 What is the functionality of glycerol in the following reactions:
(a) urethane formation with
OCN CH2 NCO
(b) esterification with phthalic anhydride (c) esterification with acetic acid
CH3 C O
OH
(d) esterification with phosgene?
1-9 How would you synthesize a block copolymer having segments with the following structures?
CH2 CH2 CH2 CH2 O
OCH2 CH2 O
CH3 C N
N C
O n
? H
H
O
m and
1-10 Write structural formulas for (a) polyethylene
(b) poly(butylene terephthalate) (c) poly(ethyl methacrylate)
57 Problems
(d) polycarbonate
(e) poly(1,2-propylene oxalate) (f) poly(dimethyl siloxane) (g) polystyrene
(h) polytetrafluoroethylene (i) poly(methyl acrylate) (j) poly(vinyl acetate)
1-11 Polyisobutene is used as an elastomer in inner tubes and some cable coat- ings. It is also used in adhesives and as an additive to adjust the viscosity of motor oils. What is the basic difference in the state of the polymer in these two different applications?
1-12 What is the functionality of the monomer shown H2N
H2C C C C
O OH CH2 CH2
CH2
CH2 CH2
(a) in a free radical or ionic addition reaction through CQC double bonds?
(b) in a reaction that produces amide links?
(c) in a reaction that produces ester links?
1-13 (a) What is the functionality of the diglycidyl ether of bisphenol A(1) in a curing reaction with diethylene triamine (2)?
1 O
H C
CH2 CH2 O C O
O
H C CH2 CH3
CH2 CH3
(b) What is the functionality of2in this epoxide hardening reaction?
2
H2N N
H
CH2 CH2 CH2 CH2 NH2
(c) Will this reaction lead to a cross-linked structure?
1-14 Show the repeating unit that would be obtained in the polymerization of the following:
(a) (b)
(c)
(d)
(e)
H2C C CH
NCO
H2N CH2 CH2 NH2 +
NCO
and H
CH2 CH3
CH2
HOCH2CH2OH and C
H H
O
HOOC H
H COOH
C
C C O
O C H
C C
H2C C H
CN
1-15 Which of the following monomers can conceivably form isotactic polymers?
(a)
(b)
(c)
(d)
(e) CH2
CH2
CH2
CH2
C O
NH CH2
CH3
CH3
HOCH2CH2OH + HO CH3
CH2 C
C C H H
CH2 CH3
CH2
CH2
C H C H
C C
O O
OH ?
59 Problems
1-16 Draw projection diagrams (planar zigzag) for
(a) the syndiotactic polymer produced by 1,2 enchainment of isoprene.
(b) isotactic poly(3,4-isoprene).
1-17 Polyethylene and polyisobutene are both hydrocarbon polymers and have intermolecular forces of similar magnitude. Yet one polymer is a plastic and fiber-former and the other is an elastomer. Comment briefly on the reason for this difference in properties.
1-18 Poly(vinyl alcohol) is made by free-radical polymerization of vinyl acetate and subsequent base-catalyzed transesterification with methanol to yield the alcohol polymer.
(a) Write an equation showing the transesterification of one repeating unit of poly(vinyl acetate) to one of poly(vinyl alcohol).
(b) Before the advent of nuclear magnetic resonance spectroscopy, one way of determining head-to-head structures in poly(vinyl alcohol) was by means of the following difference in diol reactions:
(1,2 DIOL)
(1,3 DIOL) C OH H
C CH C
OH H
C No reation OH
H C OH H
C + O H HIO4
HIO4 Solution C
O H
Solution
With a particular poly(vinyl alcohol) sample no periodic acid is con- sumed, within the limits of analytical accuracy. This indicates no apparent (1,2-diol) cleavage. However, the viscosity average molecular weight of the sample decreased from 250,000 to 100,000. Explain these results in terms of the structures of poly(vinyl acetate) and poly(vinyl alcohol). [The analytical technique is described by P. J. Flory and F. S. Leutner, J. Polym. Sci.3, 880 (1948);5, 267 (1950).]
1-19 Polyethylene terephthalate (1-5) is a crystallizable polymer which is melted and shaped at temperatures greater than 270C because of its high crystal melting point. It was thought that substitution of propylene glycol for the ethylene glycol in reaction (1-1) would produce a polyester that would still be crystallizable and hence rigid, but would also be processable at lower temperatures because of the increased hydrocarbon character of the polymer backbone. Should the glycol used here be 1,3-propane diol or the 1,2-isomer? Justify your answer briefly.
1-20 Calculate the rms-end-to-end distance for a macromolecule in molten polypropylene. Take the molecular weight to be 105, tetrahedral carbon angle5109.5, and the C—C bond length51.5431028cm. Assume free rotation.
(a) How extensible is this molecule? (That is, what ratio does its extended length bear to the average chain end separation?)
(b) Would the real macromolecule be more or less extensible than the model used for this calculation? Explain briefly.
1-21 Polymer A containsxfreely oriented segments each of lengthla, and poly- mer B containsyfreely oriented segments with lengthlb. One end of A is attached to an end of B. What is the average end-to-end distance of the new molecule?
1-22 Using the data of polyethylene given in the hindered rotation model (Section 1.14.2.3) calculate factions of CaC bonds in thetransand gauche (g2 andg1) states in a polyethylene molecule at 200C. Determine its corresponding characteristic ratio and Kuhn length.
1-23 For polyethylene, the trans conformation signifies the lowest energy state for the dihedral angles of the skeletal bonds. This leads to the experimental observation that chain dimension of polyethylene decreases with increas- ing temperature. On the other hand, for silicone polymers, the lowest energy conformations of the skeletal bonds are gauche conformations.
What would you expect the temperature dependence of the chain dimen- sion for silicon polymers to be? Briefly explain your answer.
1-24 In the Gaussian chain model, the end-to-end distance of a polymer mole- cule follows Gaussian statistics. This means that the probability that one end lies in the volume element dV54πr2dr at r from the other end is given by the following expression:
PðrÞ5 3 2πnl2
3=2
e23r
2 2nl2
where n is the number of bonds; l2 is the average squared bond length;
and r is the straight line distance between the two ends of the polymer molecule.
(a) Sketch qualitatively the Gaussian distribution function (i.e.,P(r)) and the radial distribution function (i.e., 4πr2P(r)) of the end-to-end dis- tancerfor a polymer chain with a (2nl2/3) value of 900 nm2;
(b) If the mean square end-to-end distance,r2. 5 ðN
0
r2PðrÞ4πr2dr= ðN
0
PðrÞ4πr2dr;
61 Problems
show that,r2. 5nl2. Note that ðN
0
r4e23r
2 2nl2dr5 1
4π 2π
3 3=2
ðnl2Þ5=2;
(c) Calculate the most probable end-to-end distance of the chain depicted in part (a);
(d) What is the characteristic ratio of the polymer molecules that can be described by the Gaussian chain model?
References
[1] P.J. Flory, Principles of Polymer Chemistry, Cornell University Press, Ithaca, NY, 1953.
[2] J.A. Brydson, Plastic Materials, seventh ed., Butterworths, London, 1999.
[3] H.F. Mark, Am. Sci. 55 (1967) 265.
[4] W.V. Metanomski (Ed.), Compendium of Macromolecular Nomenclature, Blackwell Scientific Publications, Oxford, UK, 1991.
[5] W. Ring, I. Mita, A.D. Jenkins, M. Bikales, “Source-Based Nomenclature for Copolymers,”
Pure Appl. Chem. 57, 1427 (1985).
[6] IUPAC Macromol. Chem. Div. (IV), Commission on Macromol. Nomenclature, Polym. Bull. 32 (1994) 125.
[7] J.C. Randall, Polymer Sequence Determination, Academic Press, New York, 1977.
[8] T. Radiotis, G.R. Brown (Eds.), J. Chem., 72, 1995.
[9] W.L. Mattice, U.W. Suter, Conformational Theory of Large Molecules: The Rotational Isomeric State Model in Macromolecular Systems, Wiley Interscience, New York, 1994.
[10] W. Kuhn, Kolloid-Z., 76 (1936) 258; 87 (1939) 3.