Pharmaceutical Drugs and Dosage: Pharmaceutical polymers - Review questions answers
Review questions
11.1 Which property is NOT
TRUE for poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) block
copolymers?
A. Surfactant
B. Forms micelles
C. Biodegradable
D. Thermosensitive
E. All of the above
F. None of the above
11.2 Which of
the following is TRUE for biomaterials?
A. The greater the
degree of crystallinity of the polymer, the lower the rate of dissolution.
B. Molecular weight and
molecular weight distribution affect sol-vent penetration and crystallinity.
C. Increase in the
main-chain polarity increases the glass transition temperature of a polymer.
D. Modification of
biomaterial surfaces with polyethylene glycol minimizes protein adsorption
and/or platelet adhesion.
E. All of the above.
F. None of the above.
11.3 Define
the following nomenclatures using chemical structures of commonly used polymers:
A. Biomaterials and
biocompatibility
B. Block and graft
copolymers
C. Repeating unit and
end group
D. Monomer and oligomer
11.4 What is
the degree of polymerization (DP) of (a) a sample of poly(methyl methacrylate) with average molecular weight of 50,000,
and (b) a sample of poly(tetramethylene-m-benzenesulfonamide) with average
molecular weight of 26,000?
11.5 Suppose we have a polymer sample consisting of 9 moles with
molec-ular weight 15,000 and 5 moles with molecular weight 25,000. What is the
number average molecular weight (Mn) and the weight average
molecular weight (Mw)?
Answers:
11.1 C.
11.2 E.
11.3 A. Biomaterials
and biocompatibility: A biomaterial is a natural or synthetic polymer used
as a device or carrier, intended to interact with biological systems.
Biocompatibility is the ability of a mate-rial to perform with an appropriate
host response in a specific application.
B. Block and graft
copolymers:
Two or more monomers are employed for
synthesizing copolymers. In copolymers, the monomeric units may be distributed
randomly (random copolymer), in an alternat-ing fashion (alternating copolymer),
or in blocks (block copoly-mer). A graft copolymer consists of one polymer
branching from the backbone of the other.
C. Repeating unit
and end group:
The structural unit enclosed by brackets
or parentheses is referred to as the repeating
unit (or mono-meric unit). To
accent the repetition, a subscript n is
frequently placed after the closing
bracket, for example, β[βCH2CH2β]nβ. End groups are the structural units that
terminate polymer chains.
D. Monomer and
oligomer:
Polymers are synthesized from simple molecules
called monomers by a process called polymerization. If only a few monomer
units are joined together, the resulting low-molecular weight polymer is called
an oligomer.
11.4 A.
Molecular weight methylmethacrylate = 100, DP= 50,000/100 = 500; molecular weight
tetramethylene-m-benzenesulfonamide =
211, DP = 26,000/211 = 123
Mn
= (15,000 * 9 + 25,000 * 5)/(9 + 5)= 18571.4
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