Content Polymers Exam 1

telomer

2-5 monometric units

oligomer

short macromolecule that consists of monomeric units. becomes a polymer when properties do not change after one additional monomeric unit

degree of polimerization

number of monomer molecules used to make the polymer chain

addition polymer

remove the double bond

condensation polymer

create a small molecule byproduct like hcl or h20.

condensation polymer example

nylon 6,6 or poly sulfone examples of 

Chain Synthesis

only growth reaction is addition of monomer to a growing chain with a reactive terminus

reaction mixture chain

highly polymer and unreacted monomers, very few actively growing chains

monomer concentration chain

monomer concentration decreases steadily as reaction time increases

molecular weight chain

high polymer appears immediately, average mw doesn’t change much as reaction proceeds 

reaction time chain

increased reaction time increases overall product yield. doesn’t affect polymer avg. mol weight

step growth polym

reaction can occur independently between any pair of molecular species

mixture step growth

oligomers of many sizes, in a statistically calculable distribution

monomers step growth

disappear early in favor of low oligomers

molecular weight step growth

oligomers steadily increase in size, polymer average mol weight increases as reaction proceeds

reaction time step growth

need long reaction time to produce polymer with high average molecular weight

LDPE and HDPE

linear and branched chains respectively make up these two types of polymers

homo polymer step

one type of repeating unith

homopolymer chain

one type of monomerc

copolymer step

more than one type of repeating unit

copolymer chain

more than one type of repeating monomer

graft copolymer

main chain same repeating units, side chains with different repeating units

thermoplastics

can be softened by head and reshaped

thermosets

cannot be reshaped by a heat treatment. different in mechanical properties, heating, solubility, and recycling

sequential IPN

create two different polymer networks separately, overlay them and they bond together

simultaneous IPN

built together on top of one another

polymer blend

macroscopically homogenous mixture of two or more different species of polymer. can be miscible or immiscible

miscible blend

one phase material

immiscible blend

two phase material

immiscible blend properties

controlled by size of phases and interaction between phases

polymer composite

multicomponent material comprising multiple different (nongaseous) phase domains in which at least one type of phase domain is a continuous phase. can include inorganic or organic polymer particles or fibers

properties polymer composite

controlled by size of inclusions, level of their dispersity and arrangement in the matrix and interaction between matrix and inclusion.

Mc-critical entanglements molecular weight

molecular weight necessary for the formation of stable entanglements

glass transition temp

lower than melting temp. temperature of transition from a glass amorphous solid state to a liquid melt state. At this temp have the onset of coordinated long-range molecular motion of polymer chain

melting temp

temperature of melting of polymer crystals.

semi crystaline

these polymers demonstrate both glass transition temp and melting temp

secondary-relaxation processes

short range motions involving several contiguous groups along the chain backbone or substituent groups below glass transition temp or between Tg and Tm

conformation

geometrical arrangement of atoms in polymer chain that can be changed without breaking of the chain

random coil

in amorphous polymer bulk and solutions, looks like a very large blob

globule

polymer chain is collapsed in smaller blob

fully extended

in crystals. straight line chain

configuration

stereochemical arrangement of atoms in a polymer chain. cannot be altered without breaking chemical bonds

chiral center

asymmetric carbon atom configuration

enantiomers

two isomers, mirror images of each other, rotate plane polarized light equally but in opposite directions. configuration

isotactic

may form crystals. same configuration each molecule

syndiotactic

alternating configuration, may form crystals

atactic

random configuration/tacticity. no crystals if non-polar

head to tail

configuration where head goes to tail of other molecule

polydispersity index

have molecular weight over number average

polydispersity index range

greater than one polymers high number different polymers. less than one high number same polymers

number average

sensitive to admixture of molecules with lower molecular weights

weight average

sensitive to admixture of molecules with high molecular weight

step growth polymerization

1. consumption of monomer 2. combination of small fragments 3. reaction of oligomers to give high molecular weight polymer

high yield chemical reactions

esterification, ester exchange, amidation

monomers step growth

each has two reactive end groups and A can only react with B and visa versa

telechelic polymer

polymer carrying reactive end groups

gelation point

important for synthesis of reactive resigns, adhesive workability, materials fabrication

network polymers

are formed from monomers having a functionality greater than two

functionality of polymers

retain their functionality as end groups at the completion of polymerization

single reaction step growth

is responsible for all steps contributing to polymer formation

molecular weight in step growth

increases slowly even at high levels of conversion. 

high mw polymer in step growth

need high yield and exact stoichiometric balance to obtain this. easier with a-b type monomer. side reactions will upset balance

k

is the rate constant and is temperature dependent

assumptions step growth

rate constant independent of chain length, increased viscosity does not affect reaction, mechanism of reaction does not change with converstion

acutallities of step growht

removal by-products difficult, polarity changes, diffusion problems in viscous system for longer molecules

interfacial

reaction goes rapidly at low temp, diffusion of monomer to interface is rate determining, similar to chain polymerization as occurs so rapidly so get higher mw, not need exact stoichiometric blanace

bulk polymerization step

low levels of contaminate high yield per reactor. dis: high viscosities, elevated temp for effective stirring and removal by-products, flow inert gas to facilitate removal by-products

solution step

low viscosities, easy to remove by-product dis: removing solvent

monomer to polymer chain

one type of reactive monomer and initiator, get polymer with residual monomer A and very small amount of growing chains

why need various initiators

t-range, solubility, end functionality

radical polymerization

association, propagation, termination

combination

combine two chains to terminate radical chain growth. flip the radical of second chain

disproportionation

terminate by by donation h+ ion from one chain and then formation of double bond in the chain that donated the H+ ion

chain transfer

radical that donated H will continue polymerization. the polymer accepted the h will have train transfer moiety at the polymer end

gel effect/ tromsdorff

occurs in bulk or very concentrated solutions, chain mobility is decreased, termination difficult, diffusion controlled, diffusion of monomer to growing chains stays intact

celling temperature

where polymerization reaches equilibrium

r1=r2=1

F1=f1 and both are constant during polymerization. truly random co-polymer

r1=r2=0

F1=f1 only when f1=0.5. F1=0.5 and stays constant during polymerization until minority monomer is consumed. f1 is not constant if it is not equal to 0.5. alternating copolymer is produced until minority is consumed

r1<1 r2<1

F1 is not equal to f1 besides azeotropic point. they are not constant during polymerization. some kind of random copolymer produced. between random and alternating, statistical

statistical

a polymer between random and alternating

r1>1 r2>1

F1 not equal f1. are not constant, homopolymers and block copolymers produced

r1 >1 r2<1

F1 is not equal to f1. are not constant. statistical copolymer produced

r1 x r2 =1

truly random copolymer, “ideal” copolymerization. F1 is not equal to f1 besides when both =1 and are both only consistent when they =1.

anionic polymerization 

propagation: insert of monomer between the carbanion and counterion. living polymerization, have to introduce termination via o2,co2,h20

electron withdrawing group

stabilizes anionic propagating species

cationic polymerization

propagation insert the addition to chain before anionic stabilizer. termination by chain transfer to monomer, polymer or solvent.

electron donating group

stabilizes cationic propagating series

unimolecular rearrangement 

the initiator takes h from chain to terminate it in cationic polymerization

radical copolymerization dependence

r1, r2, little T, and solvent

ionic copolymerization dependence

r1,r2, strong initiator, solvent and T dependence

coordination polymerization

used to obtain HDPE and isotactic polyolefins and dienes. Ziegler Natta catalysts, metal organic complexes

radical polymerization techniques

bulk, solution, suspension, emulsion

radical and cationic polymerization techniques

only solution

gas phase

coordination polymerization technique is

solid state

polymerization technique that has the polymerization of monomers in their crystalline state using heating or irradation

plasma

polymerization in ionized gas evo where pos and neg charged species and electrons are present. very good for coatings

bulk polymerization chain

high yield, easy recover polymer, possibility of casting the polymerization mixture into final product form. dis: high viscosities, diff remove last races of monomer, problem dissipating heat produced during polymerization

solution

lower viscosities, easy to remove heat dis: remove of solvent, low yield per reactor

suspension polymerization

water in-soluble monomer and initiator. excellent heat transfer. stabilizer to prevent coalescence of particles. micron droplets that serve as mini reactors with normal bulk radical kinetics. recover polymer via filtration and washing. dis: low purity with stabilizer

Emulsion Polymerization

water in-soluble monomer, water soluble initiator. surfactant. good tacky polymers. recover polymer by coagulation with salt. dis: low purity due to surfactant