Dyes, Chromophores & Auxochromes; Dye Types, Polymers & Adhesives (Lecture Notes)

Vocabulary flashcards covering key terms from dyes, chromophores/auxochromes, dye types, and polymers & adhesives.

A colored chemical that binds to fibers or foods and remains chemically stable; not every colored substance is a dye.

Dye

Chromophore

The color-bearing part of a dye molecule; contains conjugated double/triple bonds and provides the color.

Auxochrome

A substituent that does not itself impart color but increases color intensity and helps fix the dye to fabric; contains lone-pair electrons.

Chromogen

A compound that contains a chromophore but lacks an auxiliary group; color appears only if an auxochrome is present.

Golden Formula for Dyes

Dye = Chromophore (color source) + Auxochrome (color booster/fixer).

–N=N– (Azo group)

A conjugated azo linkage that acts as a primary chromophore in azo dyes.

–NO2 (Nitro group)

A nitro chromophore that helps absorb light to produce color in nitro dyes.

–NO (Nitroso group)

A nitroso chromophore present in some dyes, contributing to color.

Quinoid rings

Conjugated ring systems (quinonoid) that act as chromophores in certain dyes.

Acidic Auxochromes

Auxochrome groups that are acidic, e.g., –OH, –COOH, –SO3H, which enhance color and fixation.

Basic Auxochromes

Auxochrome groups that are basic, e.g., –NH2, –NHR, –NR2, which boost color.

Common Auxochromes

Groups such as –OH, –NH2, –SO3H, –NR2 that increase color intensity and help fixation.

NO2 memory tip

Nitro groups (–NO2) are a key chromophore in nitro dyes; mnemonic helps remember color origin.

Nitro Dyes

Dyes containing –NO2; absorb light to show color; commonly used for wool dyeing.

Naphthol Yellow

A classic example of a nitro dye used for wool dyeing.

Mordant Green 4

A nitro dye example used to illustrate dye classes and mordanting.

Azo Dyes

Dyes containing the azo group (–N=N–) as the main chromophore; often paired with auxochromes.

Auxochromes in Azo Dyes

Common auxochromes include –OH, –NH2, –SO3H, –NR2; they strengthen color.

An example of an azo dye.

Para Red

An example of an azo dye.

Congo Red

Bismarck Brown

An example of an azo dye.

Phenolphthalein

A triarylmethane dye also known as an acid-base indicator; acts as a chromophore within its structure.

Malachite Green

A triarylmethane dye used as a dye example; features a strong color due to its chromophore system.

Direct Dyes

Dyes that dissolve in water and are applied directly to cotton and other plant fibers.

Vat Dyes

Dyes insoluble in water; reduced to solubility to dye, then re-oxidized on fibers to form insoluble color.

Mordant Dyes

Dyes that require a mordant (binder) on the fabric to fix; aluminum salts are common mordants.

Disperse Dyes

Dyes insoluble in water used for modern synthetic fibers (polyester, nylon); applied as dispersed particles.

Azoic Dyes (Ice Dyes)

Dyes applied at very low temperatures to give bright, intense colors.

Alizarin

A famous anthraquinone dye used with mordants; classic mordant dye.

Anthraquinone Dyes

Dyes with anthraquinone chromophore (paired quinoid system) producing deep colors.

Indigo Dye

A vat dye with a carbonyl (C=O) chromophore; dyed onto cotton via vat method.

Indigo VAT Dyeing

Cotton dyeing using a reduction-oxidation (vat) process that fixes the dye inside fibers.

Chromophore (color source)

The part of a dye that actually provides color through its conjugated system.

Auxochrome (color booster)

Group that enhances color intensity and helps fix dye to fabric by supplying lone pairs.

Direct Dyes (application)

Dyes used by dissolving in water and applying directly to cotton and vegetable fibers.

Mordant (binder)

Substance (often aluminum salts) used to fix dye to fabric via a middleman layer.

Disperse Dyes applications

Used for modern synthetic fibers (nylon, polyester) due to insolubility in water.

Alizarin is an example of an anthraquinone dye.

Anthraquinone dyes example

Direct Dyes vs Vat Dyes vs Mordant Dyes vs Disperse Dyes vs Azoic Dyes

Categories of dyes classified by solubility and fixation method.

Indigo chromophore

Indigo’s color comes from a carbonyl (C=O) chromophore in its structure.

Dye classification by structure

Dyes are classified by structural features (chromophore/auxochrome) and by how they’re applied (direct/vat/mordant/disperse/azoic).

Polymer

A long chain formed by linking many monomers; the basis of plastics and fibers.

Homopolymer

A polymer made from a single type of monomer (e.g., polyethylene from ethene).

Copolymer

A polymer made from two different monomers (e.g., Buna-S from styrene and butadiene).

Terpolymer

A polymer made from three different monomers.

Thermoplastic Polymers

Polymers that soften when heated and harden when cooled; can be remolded (e.g., PVC, polyethylene, polystyrene).

Thermosetting Polymers

Polymers that irreversibly set on heating and do not melt again (e.g., epoxy, Bakelite).

Nylon-6,6

A polyamide polymer formed by condensation; used in textiles.

Polyester (Terylene)

A condensation polymer used in textiles and fibers.

PVC

Polyvinyl chloride; a thermoplastic polymer used in pipes and consumer goods.

Epoxy resin

A two-part reactive adhesive (resin + hardener) used in thermosetting systems.

Bakelite

Early thermosetting polymer used in electrical switches and durable coatings.

Addition Polymerization

Chain-growth polymerization where monomers add on with no by-product (e.g., PVC, polystyrene).

Condensation Polymerization

Step-growth polymerization with elimination of small molecules (e.g., water, HCl) yielding polymers like nylon and polyester.

Monomer vs Polymerization

Monomer is a single building block; polymerization links many to form a polymer.

Adhesive

A substance that bonds two surfaces together; can be non-reactive or reactive.

Non-Reactive Adhesives

Glues that bond by drying/evaporation or pressure without chemical reaction.

Solvent-based Drying Adhesives

Dissolve in solvent; as solvent evaporates, bonds form (e.g., Rubber Cement).

Water-based Drying Adhesives

Glue dispersed in water; dries as water evaporates (e.g., White glue).

Pressure-Sensitive Adhesives

Tacky glues that bond under light pressure and can be peeled off (e.g., Scotch tape, Post-it notes).

Hot-Melt Adhesives

Adhesives solid at room temperature that melt when heated and set upon cooling (e.g., glue sticks).

One-Part Reactive Adhesives

Adhesives that cure via moisture, heat, or UV without mixing (e.g., silicone sealant).

Multipart (Two-Part) Reactive Adhesives

Adhesives consisting of resin and hardener that must be mixed before use (e.g., epoxy resin, Araldite).