Polymer Chem_Exam 1 Terms

Hermann Staudinger

Won Noble prize for attributing properties of polymers to ordinary intermolecular forces between molecules of very high molecular weight

Karl Siegler & Giulio Natta

Won Noble prize for the discovery and application of new coordination catalysts for initiating polymerization reactions and the development of polymers having controlled stereochemistry

Paul Flory

Won Noble prize for establishing a quantitative basis for polymer behavior

Addition Polymerization

Chain grows by adding 1 atom on at a time

Condensation Polymerization

Involves the loss of a small molecule (H2O, HCl, CH3OH)

Monomer

Simple molecules; a single repeat unit

Repeat Unit

Identical small molecules (monomers) that repeat along the polymer backbone

Vinyl Monomer

A monomer containing a double bond

Macromolecule

Large molecule made up of simple repeating units (i.e. polymer)

Oligomer

A low molecular weight polymer with only a few monomer units joined together

Copolymer

Made from 2 ore more monomers

Alternating Copolymer

A-B-A-B-A-B

Random Copolymer

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

Block Copolymer

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

Graft Copolymer

A-A-(B-B-B-B)-A-A-A-A-(B-B-B)

B chains hang from A backbone

Linear Polymer

Straight chain polymer (many have small pendant groups)

Branched Polymer

Straight chain backbone with branches radiating off

Crosslinking

A process where linear or branched polymer chains are joined together by covalent bonds

Network Polymer

Complex polymers that are heavily linked to form a complex network

Cross-linked Polymer

Linked via covalent bonds; related to network polymer

Thermoset

Polymer cannot melt, flow or be molded because of crosslinking

Star Polymer

3 or more polymer chains branches radiating from a central core; hyperbranched

Comb Polymer

Straight chain polymer containing regularly spaced pendant chains of nearly equal length

Ladder Polymer

Linear polymer composed of recuring fused rings

Semi-ladder Polymer

Recurring fused rings interspaced with open chains

Polyrotaxane Polymer

Straight chain polymer threaded through rings

Polycatenane Polymer

Linked rings of polymers

Dendrimer

3D hyperbranched molecule; resembles star polymers but each leg has repeating branching like a tree

Convergent Dendrimer

Build dendron wedges and add to a core (outside in)

Divergent Dendrimer

Start at the core and react out (inside out)

Commodity Polymers

High volume, quick production, low cost, disposable

i.e. food containers

Engineering Polymers

Low volume, higher cost, more durable, superior mechanical properties, competes with metals, glass, and ceramics, used in industrial machinery

i.e. Tupperware

Thermoplastic

Polymers that are not crosslinked and usually dissolve in some solvent, melt and flow

Modulus

Ratio of stress to strain, which is a measure of the stiffness of a polymer

Tensile Strength

Measures the maximum stress a polymer can withstand while being stretched or pulled before breaking

Flexural Strength

Withstand bending without breaking

Toughness

Measures a polymer’s ability to absorb energy and deform without fracturing (i.e. impact resistant)

Hardness

A polymer’s resistance to localized plastic deformation (i.e. durable coatings)

Impact Resistance

The ability of a polymer to withstand a sudden force or shock without breaking

Elongation

Represents the percentage increase in length a polymer can undergo before failure (i.e. streatchability)

Creep Resistance

Describes a polymer's ability to resist deformation over time under a constant load

Fatigue Resistance

The ability of a polymer to withstand repeated loading and unloading cycles without failure

Plastics

Consumed more than iron or steel

Thermoset (hard)

Thermoplastic (soft)

Weighs less than iron or steel

More corrosion resistant than metals

Fibers

High strength and modulus

Stretchable

Food thermostability

Spinnable

100x longer than it is wide

Natural - cotton, silk, wood

Used in textiles, rope, cable, bulletproof vests

Rubber

Stretch and retract quickly

Resilient

Natural - converted by crosslinking

Man made - elastomers

Elastomer

Man made rubber

Adhesives

Natural gums and resins

Starches and cellulose nitrates

Synthetic - epoxides

Coatings

Colored clays

Paints, oils, varnishes

Degree of polymerization (DP)

Total number of structural units (including end groups)

DP = MW polymer / MW repeat unit

Step-growth

Any two difunctionalized monomers can react - most often condensation rxn

Monomer used up rapidly

Growth is slow (DP increases slowly)

Longer rxn time increases ME

All molecular species present throughout - dimers, trimers, oligomers

Chain-growth

Reaction by addition of monomer to the active chain end - most often addition rxn

Monomer used up slowly

Growth is rapid (DP increases rapidly)

Only monomer and polymer present

Number Average Molecular Weight

Mn = [sum(M*N)] / [sum(N)]

Sensitive to the total number of molecules

Weight Average Molecular Weight

Mw = [sum(M²*N)] / [sum(M*N)]

Sensitive to the highest MW species

Polydispersity Index (PDI)

Measure of distribution of chain sizes

PDI = Mw / Mn

= 1 (monodisperse)

> 1 (polydisperse)

= 1.5 (common for step-growth)

Colligative Properties

Physical changes that result from adding solute to solvent; depend on number of solute particles present as well as solvent amount

Do not depend on the type of solute particles (do depend of the type of solvent)

End Group Analysis

Determines Mn

Membrane Osmometry

Determines Mn

Semi-permeable membrane → polymer hinders movement and causes osmotic pressure

Vapor Phase Osmometry

Determines Mn

Polymer in solution has a different vapor pressure than pure solvent

Cryoscopy

Determines Mn

Freezing point depression

Ebulliometry

Determines Mn

Boiling point elevation

Viscometry

Determines Mv (viscosity MW)

Add pressure and then measure flow time

Relative method - must be compared to a standard

Light Scattering

Determines Mw

Light passes through a medium, scatters at different angles, and the intensity provides characteristics of the polymer

Ultracentrufugation (Sedimaentation)

Determines Mw

Use a slow speed to separate polymers

Gel Permeation Chromatography (GPC)

Size Exclusion Chromatography (SEC)

Determines Mn, Mw, and Mz (largest molecules make the most impact)

Large molecules come out first and small molecules come out later

Mass Spectrometry

Determines Mn and Mw

MALDI-MS (matrix assisted laser desorption ionization)

Morphology

Structure, arrangement, and physical form of polymer molecules

Mechanical Properties

Attractive forces between molecules (other polymer chains)

Dipole-Dipole Interactions

Intermediate

Intermolecular forces exerted by polar molecules on one another; partial charges; temperature dependent

Hydrogen Bonding

Strong

Attraction between partially positive H covalently bonded to a N, O, F in one molecule and a N, O, F of another molecule

London Forces (Dispersion)

Weak

Intermolecular forces exerted by molecules on each other caused by brief constantly shifting electron imbalances in molecules that act as momentary dipoles; induced dipole; important at high temperatures

Ionic Bonding

Strong

Electrostatic interaction between opposite charges

Ion-dipole

Intermediate

Interaction between a full charge and a partial charge

Crystalline

Molecules in an ordered arrangement or aligned in regular arrays

Rigid, high MP, less affected by solvent, lower impact resistance

Lamellar

Large polymers form plate-like crystals

Amorphous

Lack of order among the molecules; no tendency towards crystallinity

Lower MP, softer, more affected by solvent

Amorphous State

State of polymers at a temperature above its melting point

Vitrification

If a molten polymer that is cooled retains its amorphous state

Rheology

Science of deformation and flow of molecules with an application of force

Warming up a polymer allows the chains to move and untangle

Glass Transition Temperature (Tg)

A characteristic temperature at which glassy amorphous polymers become flexible or rubber-like because of onset of segmental motion

Plasticizer

Added to polymer to make it more flexible (lower Tg)

Stereoregularity

Monomer with an asymmetric center at the skeletal atom - this can form a stereoregular polymer

Head-to-Tail

The head of one monomer lines up with the tail of the next (all the same direction)

Tail-to-Tail / Head-to-Head

The tail (head) of one monomer lines up with the tail (head) of the next (alternating directions)

Isotactic (i)

Each chiral center has the same configuration

Syndiotactic (s)

Alternating stereocenters have the same configuration

Atactic (a)

Random stereocenters, no pattern

Crystallinity

An ordered arrangement

Highly stereoregular (little to no branching)

Highly polar groups (H-bonding, dipole-dipole)

Crystallite

Ordered (crystalline) region

Annealing

Induces crystallinity by heating under a vacuum and/or under inert atmosphere

Drawing

Stretching a polymer above Tg

Improves mechanical properties

Nucleation

If a molten polymer cools to crystalline state

Fibrils

Aggregates of small hair-like structures

Spherulites

Fibrils arranged in clusters that are in a radial pattern

Drawn Fibrilla

Drawing (pulling) forces fibrils into layers

Epitaxial

Shish kebab

Stirring solutions or stir melts as the crystallization forms (one formed on top of the other)

Chemical Crosslinking

Decreases molecular freedom by forming networks with covalent and/or ionic bonds

Physical Crosslinking

Secondary bonding attractions between polymer chains so that it behaves as a thermoplastic ‘bonds’ can break when heated by reform when cooled

Polymer Blends

Physical mixture of two or more polymers not linked by covalent bonds (just mixed together)

♺ 2 HDPE

High density polyethylene

(-CH2-CH2-)

♺ 3 PVC / V / PV

Polyvinyl chloride

(-CH2-CHCl-)