Polymers Flashcards
what is a polymer?
polymers are a specific type of macromolecule- molecules that are composed of a large number of atoms with a high molecular weight
polymers are built up of repeating units called monomers
what are the different ways a polymer can be arranged?
homopolymer
alternating copolymer
random copolymer
block polymer
graft polymer
what do the properties of polymers depend on?
property of the monomer itself
arrangment of the monomers
how the polymer chains interact with eachother and/or the environment
what can block polymers act as?
suspending agents
what is the dissolution of polymers dependant on?
polar/ non-polar
molecular weight
presence of crosslinking
crystalline or amorphous form
what is polydisperse?
polymers do not have an exact molecular weight
if polymers are sufficently polar they are also…?
likely to dissolve in water
water-soluble polymers are potentially able to…?
increase the viscosity of solvents
swell/change shape
adsorb at surfaces
insoluble polymers…
are often capable of forming thin films and are used in tablet coating, wound dressing, membranes…
what are the layers present at polymer dissolution?
diffusion layer
gel layer
infiltration layer
what are the characteristics of polymer dissolution?
slow polymer dissolution rates
existence of these layers creates opportunities for developing modified release dosage forms
the more crystalline a polymer is then the ____ the dissolution rate?
lower
what is rheology?
study of flow and deformation of matter
what is viscosity?
the resistance to flow
what is shear?
the relative motion between adjacent layers of a moving fluid
fluids that show shear are called what?
newtonian fluids
what is shear rate?
the velocity gradient over the heigh in our block of fluid
what is shear stress?
the force applied over the area of the upper surface of the block
what is the viscosity equation?
applied shear stress= viscosity x shear rate
what are the charecteristics for non-newtonian fluids?
fluid often decrease in viscosity with increasing shear rate
some fluids increase in viscosity with increasing shear rate
what is shear thinning also known as?
pseudoplastic flow
how does viscosity and polymer concentration relate?
viscosity increases with polymer concentration
low concentration of polymers?
isolated polymer chains, shape and volume determined by polymer-solvent and intra-polymer interactions
high concentration of polymers?
inter-penetrating chains
polymer movement hindered by neighbouring chains
inter and intra polymer interactions
