Chapter 35 Polymer

Chapter 35 Polymer

Content (According to AL Syllabus)

Content (According to AL Syllabus)

Content (According to AL Syllabus)

Content (According to AL Syllabus)

Introduction

Introduction

Introduction

Introduction

Introduction

Natu rall y Occurr in g Polyme rs

Ami no aci ds and protei n

Stere ochemistr y of Amino Acids

Physi cal pr opert ies of Amino Acids

Chemical pr opert ies of Amino Acids

−

−

−

−

Chemical pr opert ies of Amino Acids –NH2 is a stronger base than – COO–COOH is a stronger acid than – NH3+

Peptides, P olypept ides and prot ein

Dipeptide The (-NH2) group of one amino acid can react with the (-COOH) group of another to form an amide. The resultion molecule is a dimmer containing two amino acid units which is describes as a dipeptide. In the process, the two amino acid molecules are joined by the condensation reaction. A water molecule is eliminated.

Polyp ep tide

dipeptide

Further reaction of each end Polypeptide/protein

Structure

of p rotei ns

Polypeptide

Dipeptide

Amino acids

Carb oh ydrates

Monosaccharides

Open chain and rin g st ruct ures o f glucos e and fructos e

presence of the free aldehyde group of the acyclic form. reducing action

 

Disaccharides

Sucrosesugar cane), Maltose malt) and Lactose milk)

Glycosidic Linkage in Carbohydrates

Polysaccharides

DNA as Nu clei c aci d

Formation of the nucleotide of a DNA molecule

Syntheti c Polyme rs

Addi ti on Poly mers Formation and Uses of Addition Polymer Addition polymerization is a chemical process in which monomer molecules are joined together to form a polymer without elimination of small molecules. The resulting polymer will therefore have the same percentage composition as the reactant monomers.

1. Polyethene, or Polyethylene [PE]

Uses of polyethene Insulate telephone line Its unique electrical properties were essential during the development of radar. Plastic bags It used in supermarket for packing various food product. milk bottles and water buckets Hard and rigid, not poisonous

Me chanism fo r the additio n p oly merization: Fr ee Radical Addit ion Polymerizat io n of Ethene

The reaction mechanism consists of three stages: chain initiation chain propagation chain termination

Chain initiation

Chain propagation

Chain termination steps

Addition polymers formed from these substituted ethenes (H2C=CHX) have a range of properties predictable based on the structure of –X (non polar substituent). –X group like –CH3 or –C6H5 are soluble in organic solvents like acetone or propanone.

2. Polypropene (PP)

3. Polystyrene (PS)

4. Polyvinyl Chloride (PVC)

5. Polytetrafluoroethene (PTFE)

∀ ∀ ∀ ∀

⇒ ⇒ ⇒ ⇒

∀⇒ ∀⇒

A teflon-coated frying pan

6. Polymethyl Methacrylate (Perspex) (PMMA)

Condens atio n Polym ers Formation and Uses of Condensation Polymer

1. Polyamide

Preparation of nylon-6,6 in the laboratory

2. Kevlar

2. Dacron

⋅ ⋅ ⋅

⋅ ⋅ ⋅

⋅ ⋅ ⋅

⋅ ⋅ ⋅

3. Urea-methanal

Eff ect of Structu re on Proper tie s of Pol yme rs

Ef fect of S truct ure on Propert ies of Po ly mers

Low Density Polyethene and High Density Polyethene High Density Polyethene

Low Density Polyethene

Vulcanization of Polymers

2-Methylbuta-1,3-diene

cis

Part of a polymer chain of natural rubber

Car tyres are made of vulcanized rubber

Degradable Plastics

1. Biopolymers

(a) Paracoccus

(b) Bacillus

(c) Spirullum

2. Photodegradable Plastics

This plastic bag is made of photodegradable plastic

3. Synthetic Biodegradable Plastics

END