lab k: polymers

polymers

large molecules that form when several monomer units join together to form long chains

natural polymers

derived from nature (ex: cotton = cellulose, silk, wool, animal based, collagen)

artificial polymers

polyethylene = common plastic used for packaging, nylon = man-made synthetic fiber, polystyrene = synthetic aromatic polymer used in food service packaging, polyvinyl chloride = pvc pipes

methods of polymerization

addition and condensation

addition 

chain growth = addition of monomer units without loss of smaller molecules; monomers must contain double or triple bonds (ex: polystyrene), typically employ a catalyst to initiate the reaction and after intiation, continues as a chain reaction

condensation

step growth = reaction between two monomer units with reactive end functional groups with loss of small molecules such as water, methanol, HCl, etc. (ex: nylon-6,6 and nylon-6,10)

synthesis of polystyrene

monomer used = styrene; initiator = benzoyl peroxide; solvent = toluene

properties of polystyrene

non polar, naturally transparent, lightweight, great electrical insulatora

applications of polystyrene 

disposable cups, food packaging, optical lenses

synthesis of nylon-6,6

adipoyl chloride and hexamethylinediamine used + 2n HCl byproduct

physical properties of nylon-6,6

Strength, durability, high thermal stability

applications of nylon-6,6

Sports equipment

Industrial fabrics: tire cords, conveyor belts, seat belts

Apparel: swimsuits, jackets

Carpets, rugs

Automotive industry

synthesis of nylon-6,10

hexamethylenediamine used with sebacoyl chloride and 2n HCl removed

physical properties nylon 6,10

Good chemical resistance, low moisture absorption

applications of nylon-6,10

Electrical insulation

Medical tubing

Recreational sports equipment

Adipoyl chloride/ hexane hazard

flammable liquid + toxic by ingestion

Hexamethylenediamine/sodium hydroxide hazard

corrosive + toxic by ingestion

nylon waste

Nylon waste including the beakers’ acetone rinsings

explain suberabsorbant polymer

These polymers have a high affinity for water due to their sodium ion content. When immersed in water, the difference in sodium ion concentration between the core of the polymer and the surrounding solution in which it is immersed creates osmotic pressure. This osmotic pressure forces water molecules into the polymer lattice, to equilibrate the sodium ion concentration inside and outside the polymer lattice. This results in the polymer matrix absorbing and holding onto the water molecules to form a gel, thus demonstrating the high-water absorbency of superabsorbent polymers. Sodium polyacrylate can absorb up to 800 times its own weight of distilled water.

polyvinyl alcohol

synthetic addition polymer. It is extremely water soluble due to its hydroxyl groups (-OH) that enable it to form hydrogen bonds with other water molecules.

how does bouncy ball work

When treated with water, poly(vinyl alcohol) will absorb the water and swell to form the elastic structure of the ball. As the polymer chains absorb water, they become entangled and form a network of entangled polymer chains. This causes the water-swollen polymer matrix to now assume a solid form, within the mold.

purpose of dish soap

contains sodium lauryl sulfate, a surfactant, that lowers the surface tension of the water. This helps the water to more easily penetrate the polymer powder, ensuring even hydration. It also prevents clumping because it allows the water molecules to coat each polymer particle effectively.

Tapping the mold

helps the polymer to assume a more compact shape

polymer bouncing ball needs to be sealed in a Ziploc bag

prevent it from drying out further, as losing water gradually, could make it brittle and less bouncy over time