Amorphous Solids

Introduction

Amorphous solids are solids that have the qualities of a solid yet lack a specific geometrical layout (e.g. glass, rubber etc.). The component particles of an amorphous solid do not have a stable three-dimensional structure. Lacking the lengthy three-dimensional order of crystalline materials, amorphous solids have a more random configuration of molecules that exhibit short-range order across a few molecular dimensions. Also, the physical properties of amorphous materials differ greatly from those of crystalline materials.

In the absence of an organised three-dimensional arrangement of atoms or ions, amorphous solids are akin to liquids. The solid to liquid transformation occurs across a wide temperature range since these substances do not have a sharp melting point. Amorphous substances’ physical properties are usually isotropic, which means they are unchanged by measuring direction and have the same magnitude over all directions. This is because there exists no ordered 3-D structure.

For infringement purposes, the definition of amorphous should be one that is easily intelligible, accessible, and proven.Physical properties of amorphous substances are generally isotropic, meaning that they are unaffected by measurement direction and have the same magnitude in all directions.

Properties of Amorphous Solids

• A lack of long-range order

An amorphous solid does not have a fixed order of arrangement. They may, however, have limited areas of ordered structure i.e., short range order. Crystallites are the crystalline sections of an otherwise amorphous substance.

• There is no distinct melting point

Amorphous substances have no clear melting point and melt at a wide range of temperatures. Glass, for example, softens and eventually melts over a range of temperatures when heated. As a result, glass can be moulded or blown into various shapes. 

• The transformation from a crystalline to a non-crystalline condition

When an amorphous solid is heated and then gently cooled by annealing, it crystallises at a certain temperature. Because of this, antique glass objects seem milky due to crystallisation.

Example of Amorphous Solid

Amorphous solids include things like glass, pitch, rubber, and plastics. It has several crystalline solid qualities, including form rigidity and hardness. They do not form an ordered arrangement and melt gradually throughout a temperature range. As a result, amorphous solids such as glass, pitch, rubber, and plastics are also called supercooled liquids instead of solids.

Crystalline Solids

One type of solid-state is crystalline solids. The majority of solid substances are crystalline. Solids are substances with a melting point beyond room temperature at atmospheric pressure. Crystalline solids are solids with a regular and three-dimensional long ordered arrangement of constituent particles. Sodium chloride, quartz, diamond, and other crystalline solids are examples.

The Characteristics of Crystalline Solids

• They are symmetrical and have defined shapes.
• These are tough and unyielding.
• Their melting point is high.
• They come together to form a crystalline system.
• They are anisotropic

Types of Crystalline Solids

• Crystalline molecular solid

Van der Waals forces hold the elements of molecular crystals together. And because of these reduced forces, molecular crystals are delicate and have low melting points. These crystals can be found in carbon dioxide, methane, frozen water, and most organic hydrocarbons. This class is further divided into three groups.

•  Non-polar molecular solid

Non-directional atoms or non-polar molecules such as hydrogen, oxygen, and methane are the constituent particles of these forms of crystalline solids. And the weak London force of attraction is at work between the constituent particles.

•  Polar molecules that bind

The polarity of bonding is determined by the dipole-dipole attraction between the molecules, and the constituent particle of this form of crystalline solid is polar.

• A molecule with a hydrogen bond

These forms of crystalline solids have polar component molecules that are linked together by hydrogen bonds. Ice is an illustration of this form of crystal.

The Difference Between Amorphous and Crystalline Solids

Conclusion 

Amorphous solids offer both opportunities and problems to the pharmaceutical business, ranging from improving the bioavailability of poorly soluble medications to isolating and formulating molecules that do not crystallise and have poor physical qualities. These three case studies show the variety of challenges that come with developing amorphous APIs with a variety of behaviours ranging from “well-behaved” to “badly-behaved.”

Compounds like Compound A, which have a high Tg, strong chemical stability, and a simple isolation approach, should be relatively easy to create, but compounds like C, which have a low Tg, poor chemical stability, and a difficult isolation process, will present numerous problems. The intermediate instance is represented by compounds in which a crystalline material is turned amorphous and maybe stabilised by a carrier (Compound B); the problem here is plainly to avoid crystallisation while ensuring that the solubility advantage is retained and translated.