Experiment 26*:

SYNTHESIS AND ANALYSIS OF COMMERCIAL POLYMERS

Objectives:

To carry out step-wise condensation polymerizations to prepare a polyamide and a set of polyesters.

To compare the solubility of various synthetic and natural polymers in water, acetone, and toluene.

To determine the length of the polyamide polymer formed during the synthesis.

Natural vs. Synthetic Organic Polymers

Proteins hair, skin, tissue

Polysaccharides

cellulose, starch

Polynucleotides

DNA, RNA

Nylons Polyesters Acrylics Polyvinyls

Plastic sheeting and plumbing materials

Polystyrenes Insulating

materials

Natural Polymers

O

CH2OH

O

H

O

OH

OH

O

CH2OH

H

O

OH

OH

O

CH2OH

H

O

OH

OH

O

CH2OH

H

O

OH

OH

Starch ( (1-4) linkages)

O

CH2OH

H

O

O

OH

OH

O

CH2OH

O

OH

OH

O

CH2OH

O

OH

OH

O

CH2OH

O

H

OH

OH

H

H

Cellulose ( (1-4) linkages)

RNA

Classifications of Synthetic Polymers

Synthetic polymers are classified by their method of synthesis.

Chain-growth Step-growth

polystyrenes Polyamides Polyesters

Synthetic Method

Addition polymerization

Condensationpolymerization

Addition Polymerization

CH CH2 CH CH2 CH CH2 CH CH2 CH CH2

Styrene polystyrene

catalyst

• Two molecules combine to form long chain polymer.

• Can be linear or branched.• INITIATION: Initiator adds to C=C of styrene, yields reactive intermediate. • PROPAGATION: Reactive intermediate reactions with a second molecule of styrene, yields another reactive intermediate. • TERMINATION: Cycle continues until two reactive intermediates combine to end polymerization.

Condensation Polymerization—

Polyamides Two molecules undergo addition

accompanied by the loss of a small molecule as a by product.

Each bond forms independently of others.

Nylon 6,10

Hexamethylenediamine

Sebacoylchloride

HN

NH

H

H

ClCl

O

O

+ 2 HCl

+

HN

NN

N

H

H

O

O

H O

Cl

OH n

diamine

Diacid chlorid

e

Condensation Polymerization—Linear Polyester

HOOH

+

Phthalic Anhydride

Ethyleneglycol

linear polyester

C

O

C

O

O

CH3CO2Na

C C OCH2CH2O

O O

n

+ 2n H2O

anhydride

diol

Sodium acetate

Condensation Polymerization—

Cross-Linked Polyester

HO++ H2O

Phthalic Anhydride

glycerol

Glyptal resin

OH

OHC

O

C

O

O

CH3CO2Na

C C OCH2CHCH 2O

O O

O

CO

CO

O

C C OCH2CHCH 2O

O O

n

anhydride

triol

Sodium acetate

Properties of Polymers—Chain Structures

Linear

Branched

Cross-linked

Elastic &flexible

Rigid & Brittle

OVERVIEW Synthesize polyamide via interfacial

polymerization and determine length of fiber formed.

Synthesize linear and cross-linked polyesters.

Compare transparency, elasticity, and hardness of synthesized polymers to other provided synthetic and natural polymers.

Compare solubility of natural and synthetic polymers in various organic solvents.

SYNTHESIS—Nylon 6,10 Pour sebacoyl chloride slowly into a solution of

hexamethylene diamine.

With tweezers, grab the film which forms at the interface of the two layers and pull up slowly.

Secure the end of the fiber around a large test tube and rotate until no more fiber is produced. KEEP TRACK OF REVOLUTIONS!

Rinse nylon in beaker of tap water, remove from test tube, and set aside for product analysis.

SYNTHESIS—Linear and Cross-Linked Polyesters

Cover watch glasses with foil and label.

Place phthalic anhydride and sodium acetate in center of watch glass and mix solids with glass rod.

Add glycerol to one, ethylene glycol to the other.

Heat and mix with glass rod until mixture becomes clear and boils.

Remove from heat and cool to RT.

Remove polymer from foil and set aside for product analysis.

ANALYSIS—NYLON FIBER LENGTH

Measure the diameter of the test tube used to collect the nylon fiber.

Determine the length of the fiber produced using the following formula:

Nylon produced (mm) = (Diameter of test tube) * ( ) * ( # test tube revolutions)* Where = 3.14

Table 26.1: Nylon Fiber Analysis

Test tube diameter (mm)

# of test tube revolutions

Length of nylon (mm)

ANALYSIS—SOLUBILITY TESTING

Label 18 small test tubes 1A-F, 2A-F, and 3A-F.

Measure 3 mL of the appropriate solvent to the test tubes.

Add a small amount of the polymer as indicated in Table 26.2.

Shake to mix the contents completely.

Record the solubility of each polymer in Table 26.2.

ANALYSIS—SOLUBILITY TESTING

1A

1B

1C

1D

1E

1F

2A

2B

2C

2D

2E

2F

3A

3B

3C

3D

3E

3F

1 = AcetoneA-F = Polymer type

2 = TolueneA-F = Polymer type

3 = MethanolA-F = Polymer type

Table 26.2: Physical Property and Solubility

ResultsPolymer Type and Solvent

IMF(circle all

that apply)

Predicted Solubility

(circle all that apply)

Observed Solubility

1 2 3Aceton

e(Sol.

or Insol.)

Toluene

(Sol. or

Insol.)

Methanol

(Sol. or Insol.)

Synthetic

A Polyamide LDF DD 1 2 3HBA HBD

B Linear polyester LDF DD 1 2 3HBA HBD

C Cross-linked polyester LDF DD 1 2 3HBA HBD

D Polystyrene LDF DD 1 2 3HBA HBD

Natural E Starch LDF DD 1 2 3HBA HBD

F Cellulose LDF DD 1 2 3HBA HBD

Solvent 1 Acetone LDF DD ***In the final lab report, copy/paste this table into your document, and circle the appropriate IMF and solubility predictions by hand. Observed solubility entries can either be typewritten or handwritten.***

HBA HBD2 Toluene LDF DD

HBA HBD3 Methanol LDF DD

HBA HBD

SAFETY

Sebacoyl chloride, hexamethylenediamine, and sodium hydroxide are CORROSIVE!

Hexane, ethylene glycol, and toluene are TERATOGENIC!

Toluene, acetone, hexane, and methanol are highly FLAMMABLE!

WASTE

All liquid waste generated throughout the course of the synthesis and solubility testing can be placed in the “LIQUID WASTE” container.

Solid polymer waste and aluminum foil can be placed in the YELLOW SOLID WASTE CAN at the front of the room.

CLEANING

All glassware used during this experiment requires cleaning with SOAP, WATER, BRUSH followed by a final rinse with WASH ACETONE.

DO NOT return any glassware to lab drawer dirty or wet !

IN LAB QUESTION(The following question should be answered in the laboratory

notebook.)

Differentiate between a chain growth addition reaction and the step growth condensation reactions used to produce the polymers described in this experiment.

Give an example of a polymer produced using each method.

IN LAB QUESTION(The following question should be answered in the laboratory

notebook.)

List the intermolecular forces present in polystyrene, toluene, and nylon. Explain, in terms of IMF, why polystyrene is soluble in toluene, but nylon 6,10 is not.