Ex 3 L1: Intro to Polymers

Question 1

History of Polymers

Answer 1

Nitrocellulose (“guncotton”, 1845)
-The first semisynthetic polymer
-Christian Schonbein (Basel, Switzerland) in his kitchen

Bakelite (1907)
-The first synthetic polymer based on phenol and formaldehyde
-Leo Baekland
-Strong and durable
-Substitute for parts in auto and electric industries

Question 2

History of Polymers 1933 and up

Answer 2

Polyethylene (1933)
-To insulate radar equipment for airplanes

Poly(vinyl chloride (1933)
Polystyrene (1993)
Polyamide (1935)
-Nylon (Wallace Carothers at DuPont) to replace silk, used in parachutes
Teflon (1938)
-Used in atomic bonds to isolate hot isotopes of uranium
-Synthetic rubbers (1942)
-1h to synthesize (7 years for natural rubbers)
-Tires, military supplies

Question 3

Shortage of _ during WW2 as synthetic polymers were needed for the war

Answer 3

Stockings/nylons

Question 4

Polymers in Pharmaceutical and Biomedical products

Answer 4

Controlled drug delivery
-(degradable vs nondegradable)
Scaffolds for tissue engineering
Oral drug delivery
-Coating
-Binders
-Taste maskers
-Protective agents
Transdermal patches

Question 5

Polymer basics

Answer 5

“polymer”
-a large molecule made up of many small repeating units parts

Question 6

Macromolecules

Answer 6

Any large molecules (not necessarily those made of repeating units)
Polymers are a subset of macromolecules

Refers to the largeness of the polymer

Question 7

Plastics

Answer 7

Plastic materials that can be molded, cast, extruded, drawn, thermoformed, or laminated into a product

Pliable, flexible up to a certain temp

Question 8

Polymer Basics: Characteristics

Answer 8

Natural vs synthetic
Name
Structure
Synthesis
MW
Crystalline vs amorphous
Glass transition temp
Mechanical properties
Applications

Question 9

Natural polymers

Answer 9

Nucleic acids (DNA, RNA)
-Amino acids
Proteins (gelatin)
Polysaccharides (cellulose, chitosan, alginic acid)

Question 10

Synthetic Polymers

Answer 10

Polyethylene; poly(vinyl chloride); poly(tetrafluoro ethylene) (aka Teflon); polyurethane; polyacrylate; poly(p-phenylene terephthalamide) (AKA kevlar)
Nylon; silicon rubber; rayon

All have poly in the name

Question 11

Polymer name

Answer 11

repeating units
-Poly (repeating unit)
-Ex: poly (ethylene glycol) - ethylene glycol is repeating unit - sometimes we use parenthesis, sometimes we don’t
-poly human
-Poly (cute child)
-Not poly(cute children)

Question 12

Polymer name acids

Answer 12

Poly(acrylate)
Poly(methacrylate)
Poly(methyl meth acrylate)
Poly(hydroxyethyl meth acrylate)

Question 13

Structure

Answer 13

Homopolymer
-Building block all the same

Random Co-polymer: Two different types, arranged in random structure

Alternate copolymer:
Two different types, one after the other

Block copolymer:
Split in half (one block of one polymer, one block of the other polymer)
-IMPORTANT

Graft copolymer:
Branch of another type attached to the parent chain

MW, and arrangement play a BIG factor

Question 14

Building blocks of polymers

Answer 14

Gelatin
-Amide bond

Polyethylene
-CH2 x 2 (ethylene = building block)

Teflon
-CF2 x 2

DNA
-One side Long Nucleic acid
-Nucleic acids are the building blocks

Amylose
-Sugar molecules (monosaccharides) are the individual building blocks)

Question 15

Polymer Synthesis: Condensation Polymerization

Answer 15

AKA: step polymerization
-Two or more (bifunctional) monomers carrying different reactive functional groups interact with each other
Ex: Nylon

Small groups of polymers

Question 16

Polymer Synthesis: Addition Polymerization

Answer 16

AKA:
-Free-radical polymerization
-Chain polymerization

-Initiation (initiated by a radical)
-Propagation
-Termination (terminated by an inert molecule)

-E.g. , polyacrylate, polystyrene

Large chain polymers

Question 17

Molecular weight

Answer 17

-Number average (Mn)
Weight average (Mw)

Question 18

Molecular weight distribution

Answer 18

Monodispersed
(Mn = Me, polydispersity (Mw/Mn):1)

Polydispersed
(Mw&raquo_space; Mn, polydispersity&raquo_space; 1)

Closer to 1 = fairly homogenous

Polydsipersion is a measure of how broadly/narrow we distribute the drug - want closer to 1

Question 19

Crystalline

Answer 19

-Linear polymer
-Polymer can pack together in regular arrays at T<Tm
-Manifests a sharp Tm
-Good barrier to drug diffusion; durable

Very well arranged

Question 20

Amorphous

Answer 20

-More common
-Polymers w/irregular structure
-Polymer forms “glass” at T<Tg
-Softens over a wide temperature range (Tg)

Hose is a polymer
-If you leave it alone in the winter, very rigid, can break = polymer

Volume above specific temp = enthalpy (amorphous)

Chaotically arranged (noodles)

Question 21

Glass transition temp

Answer 21

Temperature range where a polymer changes from a hard, rigid, or “glassy” state, to a more pliable, compliant, or “rubbery” state
-At T &laquo_space;Tg: Polymers are hard, stiff, and glassy
-At T&raquo_space;Tg: Polymers are rubbery and may flow

Question 22

Example of dosage form of Glass transition temp

Answer 22

Chewable - Nicotine gum
-Contain a polymer with Tg close to 37 deg. C so that the gum is softened at mouth temp
-Chewing: release nicotine quickly
-“Parking” between cheek and gums: slow down nicotine release

Question 23

Factors affecting Tg

Answer 23

Polymer length: The longer, the higher the Tg

Side chains: The bulkier, the higher the Tg

Crosslinking: The more crosslinked, the higher Tg
DO NOT STORE IN BATHROOM - heat humidity

Plasticizers:
-Molecules that increase the entropy and mobility of the polymer chains
-Lower Tg when included in polymer products
e.g. - water

Question 24

Mechanical properties

Answer 24

Stress (force/area) vs strain (defomration)

Slope (stress/strain): Modulus (or stiffness)

AUC: Toughness

Elastic polymers (e.g. fibers, or highly crosslinked polymers)
-Linear stress vs strain curve up to a breaking point (deform limitation)

Rubbers or elastomers
-May deform 10-15 times their original lengths

X axis: Strain - How long we are trying to stretch (energy to break)

y axis - stress; (strength to break)

Question 25

Hydrogels

Answer 25

Crosslinked networks of hydrophilic polymers
-Chemical gels (covalently crosslinked)
-Physical gels (crosslinked via hydrogen bonding, hydrophobic interaction, or complexation)

Swell rapidly when placed in water
-Chain-water interaction
-Electrostatic interaction
-Osmotic forces

Retain large volume of water in their structures

Common: polyethylene gel, agar gel
-Both are polymers soluble in water

Example: wound dressing

Question 26

Polymers in dosage forms

Answer 26

Polymers are EVERYWHERE

Cellulose-based polymers
-Ethylcellulose (tablet coating)
-Carboxymethyl cellulose (super disintegrant; emulsifier)
-Hydroxypropyl methyl cellulose (tablet binder, coating)

Hydrocolloids
-Alginic acid (thickening agent in suspension)
-Chitosan (mucoadhesive dosage forms)

Water-soluble synthetic polymers
-Poly(ethylene glycol) (plasticizer, suppository base, stealth coating)
-Poly(vinyl alcohol) (tablet binder, coating)

Water insoluble synthetic polymers
-Poly(lactic-co-glycolic acid) (controlled drug release)
-Polylactic acid (controlled drug release)