kevchan's version from 2015-10-25 23:59


Question Answer
Cellulose is known as a structural polymer for plants
Starch is known as aenergy reserved polymer for plants
A linkage instarch allows flexibility in the backbone
B linkagein cellulose allows backbone to be rigid
Small molecules undergo polymerizationto become polymers
Polymers areare repeated units that are covalently bonded to each other.
Polymers have many potentialintermolecular interaction sites
Degree of polymerization isthe number of monomeric units in a macromolecule
Topology Polymers can belinear, branched and cross-linked
Polymer Morphologyform when polymer chains are aggregated together
Free radical polymerizationinitiation, propagation and termination
FRP Initiationwhen a chain is initiated by free radical
FRP Propagationeach time a free radical hits an ethene molecule a new longer free radical molecule is formed
FRP Terminationtwo radicals hit each other producing a final molecule. No new radicals are formed. Chain termination is random so polymer chains can be all different length.
Step growth polymerizationReaction between functional groups where either two monomers come together to create a repeat unit or two difunctional monomers come together to form two repeat units.
Functionality of two isa branched polymer
Orders polymers showsymmetry like in crystals
Semi-crystalline morphologyhas both amorphous and crystalline regions


Question Answer
Temperature strongly influencesthe mechanical response of polymeric materials
Glass transition temperature is wherelarge segmental motion from thermal energy occurs related to the movement of polymeric chains
Besides increasing temperature to cause large segmental motionwe can add plasticizers to "loosen" intermolecular interactions amongst chains, and change packing of chains
If a polymer behaves like a thermoplasticheating the polymer adds thermal energy and collective motion of chain segments
Collective motion of chain segments causes the material to become soft (moving from a glass state to a rubbery state), this temperature is calledglass transition temperature
Free volumeunfilled volume at the end of a polymer chain.
Presence of a plasticizer causeschange in free volume and distrupts interaction between chains
Materials can display both brittle and ductile behavior atabove and below the glass transition temperature/ melting temperature
Cellulose is a thermoset whereit is cured and do not flow when heated because each chain is linked with another forming a network.


Question Answer
2 glucose units combine to makecellubiose where one glucose unit is flipped upside down
starch is composed of two biopolymersamylose and amylopectin
Amylose is a linear polymer ofalpha 1-4 linked glucose units
amylopectin is a branched polymer of alpha 1-4 lined glucose units but also has branches linked at alpha 1-6
Question Answer
amylopectin is a branched polymer with crystallinity becauseit has very long branches.
amylopectin formssemicrystalline particles
cellulose is always found asbundles of microfibrils in nature
intra- and inter-h-bonds chains together
cellulose chains are packed together ina "semicrystalline form"
cellulose bundles are excellent reinforcementfor the wood cell wall
Cellulose pulp is forpaper, tissue, tool handles, medical membranes
Delignification removes mostlignin
Use of pulp in chemical industry is impacted bypurity and average degree of polymerization of cellulose
Highest purity pulps requires significant bleaching with oxidate chemicals cause large environmental impact.
Strong intermolecular forces hold cellulose bundles together
Cellulose can be dissolved in novel/exotic highly polar solvents :dimethylacetamide with LiCl, M-methlymorphine oxide (lyocell process), ionic liquids
Question Answer
To dissolve in typical organic solvents mustmodify into derivaties - cellulose acetate
Cellulose ethers can dissolve in water to makecarboxymethyl cellulose, hydroxyethycellulose
Very difficult to disrupt bundles and utilize


Up to 1/3 of biomass is composed of hemicelluloses
Hetero-polysaccharides play important function in the cell wall during lignification as well as serve in the interface between the cellulose fibrils and lignin
Question Answer
Hetero-polysaccharides made up of more than one type ofmonosaccharide unit
Cellulose is made up of onlyglucose units
Short chains200 units
Hetero-polysaccharides have a branched topology and amorphous morphology in their native state
Hetero-polysaccharides have "charged" functional groups
Hetero-polysachardies can be partially acetylated and partially methoxylayed
Some polysaccharides contain 5-carbon sugars in a pyranose ring (6 member) and osme contain a 5-carbon sugar in a furanose ring (5-member
Question Answer
xyloselike cellulose except only missing sixth carbon
arabinoseas a furanose ring in L configuration
mannosehydroxyl in axial position at the 2 carbon
galactosehydroxyl in axial position at the 4 carbon
softwood polysaccharidesgalactoglucomannan, arabinoglucuronoxylan, galactan
hardwood polysaccharidesglucoronoxylan, glucomannan
cellulose and glucomannan areclosely associated.
Lignin and xylan areclosely associated
Many hetero-polysaccharides can beextracted and solubilized in alkali
Sulfite pulping and acidolysis conditions can breakdown hemicelluloses significantlyhemicelluloses are very sensitive to acids, xylan can become deacetylated and generate acetic acid and acid group can attack glycosidic linkages forming oligosaccharides
retention of hetero-polysaccharides can impact paper yield and paper properties.