Polymer Fundamentals- ALL NOTES Flashcards
What are polymers?
-Specific types of macromolecules that are made up of repeating units called monomers
What are the different types of polymer structures ?
-Homopolymer, alternating copolymer, random copolymer, block copolymer, graft copolymer
What is a graft copolymer?
What influences the properties of polymers ?
-Properties of the monomer itself, arrangement of monomers and polymerisation of monomers and polymerisation number, how the polymer chains interact
What is cross linking?
-Bridges between straight chain polymers that changes the properties of the polymer
What are the differences between polymers and small molecules?
-Polymers will only exist as solid or liquid, polymers are typically more viscous, dissolution of polymers depends on more factors eg. molecular weight, cross linking, crystalline form, polymers have average molecular weight
How do you calculate the average molecular weight (Mn) of polymers?
-(moles x mw) + (moles2 x mw2) …/ sum of moles
What is Mn?
-Number average molecular weight is the number of moles we have of Mw 1 and so on divided by total number of moles
What is Mw?
-Weight average molecular weight is the weight of all the molecules multiplied by molecular weight then divided by the total weight
What is the degree of polydispersity?
-Molecular weight/ molecular number
What effect can water soluble polymers have?
-Increase viscosity of solvents, swell/change shape, adsorb at surfaces
What are the uses of insoluble molecules?
-Tablet coating, wound dressings
What are the layers involved in the dissolution of polymers?
-Infiltration, gel and diffusion
What factors impact solubility?
-Polymer molecular weight and polymer crystallinity
What are the derivatives of cellulose that have use in pharmaceutics ?
-Cellulose-cardboard packaging
-Methycellulose
-Hydroxypropyl methylcellulose- hympromellose and film coated tablets
What are the uses of dextran?
-Active ingredient - artificial tears, emergency blood plasma expander and anticoagulant
What happens to a ph-sensitive polymer while unionised?
-Groups repel so expanded structure so increased viscosity
What is rheology?
-Study of the deformation and flow of matter
What is viscosity?
-The resistance to flow-high viscosity means reduced flow
What is shear?
-The relative motion between adjacent layers of a moving fluid
What is the symbol for rate of flow ?
-Gamma
What is the symbol for viscosity ?
-eta
What are newtonian fluids?
-Fluids whose rate of flow is directly proportional to the applied stress
What is shear rate (gamma)?
-The velocity gradient over the height in the ‘block’ of fluid
What is sheer stress (sigma)?
-The force applied in N over the area of the upper surface of the block
What is sheer thinning ?
-Fluids that often decrease in viscosity with increasing shear rate
What is shear thickening ?
-Fluids that increase in viscosity with increasing shear rate
What happens at a molecular level during shear-thinning?
-high molecular weight molecules become entangled and resist flow, with shear stress eg shaking the bottle, the molecules align with the direction of flow
What is plastic or Bingham flow?
-Some fluids only flow after a certain amount of shear stress has been applied
What happens to viscosity of molecules at low concentration?
-Isolated polymer chains, shape and volume determined by polymer solvent and interactions
What happens to viscosity of molecules at high concentrations ?
-Inter-penetrating chains, polymer movement hindered by neighbouring chains
How can viscosity be measured according to BP?
-Capillary viscometer for newtonian and rotating viscometer for newtonian and non-newtonian
How does a capillary viscometer work?
-Flow of fluid through a small tube under gravity is measured, apparatus clamped in water bath at desired temperature, suction applied to other tube to pull liquid up then measure time it takes to flow from one mark to the other
How does a rotating viscometer work?
-One cylinder with the fluid being investigated inside then solid mass inside, second cylinder is rotated at consistent speed and drag exerted on a body measured
What is the primary pack?
-The packaging that is in direct contact with the drug itself
What are the features of secondary packs?
-Contain the primary pack and any other components needed, made of paperboard generally, protects against mechanical damage and protect against light
What are the features of glass as pharmaceutical packaging?
-Different types available based on properties, can be moulded into different shapes, widely recycled.
What are the two main types of glass used in packaging?
-Neutral glass
-borosilicate glass
-soda-lime-silica glass
-silica containing alkali metal oxides
What are the types of plastic polymers used in packaging?
-Amorphous and crystalline/ semi-crystalline
What are amorphous plastics?
-Eg. PVC, have good transparency, can be made more flexible for infusion bags, some permeability to water and organic vapour
What are crystalline polymers?
-Eg. PVDC, tough and stiff, good heat resistance, chemically inert
What are commonly used plastics in pharmaceutics?
-PVC, PP (polypropylene), HDPE (high-density polyethylene), polyethylene terephthalate (PET)
What are the advantages of using metal in packaging?
-Mechanically strong and shatterproof, able to withstand heat, impermeable to light, liquids and vapours
What is an issue with using metal packaging?
-Expensive, heavy and can react with medicine
What metals are used in packaging?
-Aluminum, tinplate
