biopolymers

what are biopolymers and how is this different to biorenewable polymers

biopolymers are polymers which already exist in nature

biorenewable polymers use monomers from natural sources

give 3 examples of biopolymers

polysaccharides

polynucleotides (DNA/RNA)

proteins

advantage of biopolymers

their production is inherently renewable

give 3 disadvantages of biopolymers

can be costly

their extraction can be environmentally negative

their consistency is reduced compared to synthetic polymers

show common structure of sugar molecules

(don’t need to know any exactly, just see similar parts seen in all sugars)

show a mechanism for polymerisation with itself

describe the bond that links them

forms an ether linkage at the 1-position of the ring

what is a monosaccharide

one sugar unit

what is a disaccharide

2 sugar units

what is an oligosaccharide

polymer of sugars

what is a carbohydrate

other name for an oligosaccharide

monomer of cellulose

glucose

how are cellulose monomers linked

β-1,4-glycosidic linkages

show polymerisation to cellulose

show key intermolecular force in cellulose

geometry of cellulose

linear polysaccharide

what does the hydrogen bonding in cellulose lead to

chains form tightly packed microfibrils through extensive hydrogen bonding

where does strength and flexibility arise from in cellulose

highly ordered crystalline regions provide strngth

amorphous regions add flexibility

strength of cellulose compares to synthetic fibres?

type of strength?

high tensile strength - stronger than many synthetic fibres

solubility of cellulose

insoluble in water and most solvents

hydrophilicity/hydrophobicity of cellulose

exhibits hydrophilicity, yet maintains structural integrity when hydrated

thermal stability of cellulose

excellent thermal stability, and low coefficient of thermal expansion

where is cellulose extracted from

woodfibre

how is cellulose extracted

wood gets chipped and cooked to separate cellulose and lignin

cellulose is then bleached

applications of cellulose (2)

• 90% of cotton fibre is made from cellulose

• paper is produced by pressing together moist cellulose fibres and drying them into flexible sheets

what are 2 modifications that could be made to cellulose to obtain new properties

turn hydroxyl groups into ethers or esters

how does turning the hydroxyl groups into ethers or esters change the properties?

are all hydroxyl groups modified?

disrupts the hydrogen bonding network between sugars and makes the polymers less crystalline

not all modified

show product if hydroxyls converted to ethers

assume 2 extra carbons in chain

name the molecule

show product if hydroxyls converted to esters

name the molecule

additional reagent needed for this synthesis?

show curly arrow mechanism

solubility of hydroxyethyl cellulose

disrupting the H bond network between sugars makes the polymer more water soluble

applications of hydroxyethyl cellulose

pharmaceuticals - used as a thickener in tablets

cosmetics and personal care - used in shampoos, conditioners and liquid soaps to improve texture and spreadability

additional reagents needed for synthesis of acetyl cellulose

give mechanism for this conversion

solubility and thermoplasticity of acetyl cellulose

remains water insoluble

thermoplastic and film-forming - used for strength and transparency

applications of acetyl cellulose

textiles - clothing linings and draperies

films and plastics - transparent sheets, packaging films

monomer of chitin

structure of chitin

polymer geometry?

linear polymer of N-acetylglucosamine

where is chitin found

primary component of cell walls in fungi and exoskeletons of crustaceans

structure and formation of chitosan

made from the partial deacetylation of chitin

ionic? what type? pKa?

cationic polyamine with relatively low pKa

adheres to? reaction with polyanions?

chelation?

adheres to negatively charged surfaces, forms gels with polyanions

chelates to transition metals

formation of hydrogel?

can form a hydrogel with pH adjustment

how can chitosan be obtained

from food waste

4 steps in synthesis of chitosan, with conditions for each

(no structures)

1. decalcification: dilute HCl

2. deproteination: dilute NaOH

3. decolourisation: 0.5% KMNO₄ and oxalic acid

4. deacetylation: conc. NaOH

major application of chitosan?

• disposal?

adhesive of band-aids

1000x thinner than plastic wrap, can effectively treat injuris to soft organs such as the lungs

breaks down naturally after healing and becomes invisible within one month

what is starch made from

amylose

what is starch used for in nature

storing energy

degradation of starch

compare to cellulose

less chain packing than cellulose = more flexible, more water soluble and degrades more easily

used as a thickening agent

structure of hyaluronic acid?

where is hyaluronic acid found

animal tissue

how can hyaluronic acid be produced

microbial fermentation

retention of hyaluronic acid

can retain up to 1000x its own weight

use of hyaluronic acid

used extensively in the cosmetic industry