DOC BROWN'S Science-CHEMISTRY HOMEPAGE KS3 SCIENCE QUIZZES and WORKSHEETS (~US grades 6-8)
GCSE SCIENCE help links GCSE ADDITIONAL SCIENCE help links
KS3 BIOLOGY Quizzes KS3 CHEMISTRY Quizzes & Worksheets KS3 PHYSICS Quizzes
KS4 Science GCSE/IGCSE CHEMISTRY NOTES (~US grades 8-10) KS4 Science GCSE/IGCSE CHEMISTRY QUIZZES and WORKSHEETS (~US grades 8-10) ADVANCED LEVEL CHEMISTRY QUIZZES and WORKSHEETS (~US grades 11-12)
Custom Search

 Doc Brown's Chemistry Revision Notes - Smart Materials and Materials Science

PART 1 CHROMOGENIC MATERIALS - Thermochromic, Photochromic & Electrochromic Materials, Halochromic materials


ALPHABETICAL LIST of materials, effects etc. mentioned on these pages: Smart Materials Science INDEX * CARBON FIBRES * CHROMOGENIC MATERIALS * ELECTROCHROMIC MATERIALS * GORETEX * HALOCHROMIC MATERIALS  * HIGH PERFORMANCE POLYMERS * KEVLAR * LYCRA * MAGNETIC SHAPE MEMORY ALLOYS * MAGNETOSTRICTIVE MATERIALS * NITINOL * pH SENSITIVE POLYMERS * PHOTOCHROMIC MATERIALS * PHOTOMECHANICAL MATERIALS * PIEZO ELECTRIC EFFECT-MATERIALS * PTFE * SELF-HEALING MATERIALS * SHAPE MEMORY ALLOYS * SHAPE MEMORY POLYMERS * SPANDEX * TEFLON * TEMPERATURE-RESPONSIVE POLYMERS * THERMOCHROMIC MATERIALS * THINSULATE *


Part 1a CHROMOGENIC MATERIALS-

Thermochromic, Photochromic & Electrochromic Materials, Halochromic Materials

  • Chromogenic materials change colour in response to an electrical, optical (e.g. light intensity) or thermal changes (i.e. temperature changes).

    • A chromogen is a coloured compound containing a chromophore - responsible for the observed colour.

      • A chromophore is a group of atoms within a larger molecule that are principally responsible for the absorption of visible light to give the compound its colour. The colouryou observe is formed from the visible light that is transmitted or reflected by the chromogen.

  • There are a number of different sub-categories of chromogenic materials e.g.

    • ELECTROCHROMIC MATERIALS change their colour or opacity (how much light they let through) on the application of a voltage.

      • This effect is used in liquid crystal displays.

      • The term electroluminescence is also used to describe this effect.

      • Electroluminescent materials can produce brilliant colours if stimulated by an a.c. current.

      • Electrochromic materials can be used to light strips for decorating buildings and for industrial and public vehicles displays e.g. of safety notices.

    • THERMOCHROMIC MATERIALS change in color depending on their temperature.

      • Thermochroism is the change in colour of a material with change in temperature.

      • Thermochromic materials change colour reversibly with changes in temperature i.e. rise or fall in temperature.

      • They can be designed to change colour happens at a particular temperature, which can be varied by doping the material with other compounds.

      • Thermochromic materials are used to make paints, inks or are mixed to moulding or casting materials for different applications.

      • For example, you can coat a mug with a picture of thermochromic materials of different colours, but with a similar transition temperature. Therefore at room temperature (COLD) you see little if anything, but when you pour a hot drink into it, at a certain temperature e.g. 35oC, the thermochromic materials change colour and the 'advert' appears.
      • Designers think these are great materials for creative experiments e.g. shirts that change colour with temperature!
      • Simple 'strip' thermometers that change colour with rise in temperature, so you a colour-temperature scale!
    • PHOTOCHROMIC MATERIALS change colour in response to the intensity of light.

      • The term photochromic is applied to materials whose transmittance to light varies with the intensity of the incident light on it, so photochromic inks respond to changing light conditions.

      • Photochromic materials reversibly change colour with change in light intensity. They are often colourless in a subdued light but when sunlight or ultraviolet radiation is applied the molecular structure of the photochromic material changes and produces a different colour. When the uv/visible light source is removed the colour disappears (hence the term 'reversible').

      • Changes from one colour to another colour are possible by mixing photochromic colours with base colours which can be used in paints, inks etc. for many different applications.

      • Light sensitive sunglasses darken in response to increased intensity/brightness of sunlight and so reducing glare e.g. when driving a car or when skiing at high altitude when the snow reflects extra light into your eyes.

      • Light sensitive photochromic materials are used in optical memory devices.

      • Clothing can incorporate thermochromic inks that have patterns that change with change in light conditions.

      • For commercial use e.g. in consumer products (especially food) the photochromic inks must pass food container and packaging health and safety standards, and the producer must truthfully claim that they do not contain and potentially harmful or toxic substances.

  • -


Part 1b. HALOCHROMIC MATERIALS

  • Halochromic materials that change colour if the ambient acidity changes i.e. in contact with an aqueous solution whose pH may change over time.

  • One possible application is to use paints that can change colour in response to corrosion in the metal underneath them e.g. in the rusting of iron or steel the pH of the water in contact with the metal changes in pH.


Revise for KS4 Science GCSE/IGCSE/O level Chemistry Revision Notes for information studying revising for AQA GCSE Science, Edexcel 360 Science/IGCSE Chemistry & OCR 21stC Science, OCR Gateway Science  (and courses equal to US grades 9-10) and Revision notes for GCE Advanced Subsidiary Level AS Advanced Level A2 IB Revise AQA OCR Edexcel Salters CIE revising courses for pre-university pre-U students (equal to US grade 11 and grade 12 and Honours/honors level courses)


Nanomaterials including carbon nanotubes, carbon fibres and silver nanoparticles are on a separate page

More on chemistry applications: Uses of 220+ chemical elements, compounds, mixtures & Formulation chemistry


WHERE NEXT?

INDEX of SMART MATERIALS PAGES

PART 1 CHROMOGENIC MATERIALS - Thermochromic, Photochromic & Electrochromic Materials

PART 2 SHAPE MEMORY ALLOYS e.g. Nitinol & Magnetic Shape Memory Alloys

PART 3 SHAPE MEMORY POLYMERS, pH and temperature sensitive-responsive polymers, Self-healing materials

Part 4 LYCRA-SPANDEX

PART 5 High performance polymers like KEVLAR

PART 6 GORETEX, THINSULATE and TEFLON-PTFE

PART 7 PIEZOELECTRIC EFFECT (PIEZOELECTRIC MATERIALS) and PHOTOMECHANICAL MATERIALS

PART 8 CARBON FIBRES

See also INDEX NANOSCIENCE-NANOCHEMISTRY pages


Teach yourself chemistry online ALPHABETICAL SITE INDEX for chemistry

Advanced Chemistry Page Index and LinksWebsite content copyright Dr Phil Brown 2000-2013 All rights reserved on revision notes, images, puzzles, quizzes, worksheets, x-words etc. * Copying of website material is not permitted * chemhelp@tiscali.co.uk

Alphabetical Index for Science Pages Content A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

SITE HELP SEARCH - ENTER SPECIFIC WORDS/FORMULA etc.