Types of Self-Assembly Structures Flashcards
What are Self-Assembled Monolayers?
Organic molecules deposit as a well-ordered, single layer from solution onto a substrate.
How can you control properties of an SAM?
By changing binding groups or length/structure of organic chain and functionalisation.
Why is surface energy affected by organisation of molecules on an SAM?
Due to more/less steric hindrance in different areas.
Describe one way to form a SAM
Dip-pen Nanolithography: AFM tip with molecules on it moves across substrate and deposits molecules across water meniscus.
Give and explain 3 applications of SAMs
-Anti-static friction coating on small engineering parts that are close together (static friction causes attractive + repulsive forces b/w components, therefore can make neutral by applying coatings)
-Biomimetic Membranes: used to see how diff molecules/ions/drugs will penetrate through the membrane
-Lithography: make holes in polymer layer by removing molecules from specific places, forming a polymeric mask/template.
What are block copolymers?
A hydrophobic polymer and a hydrophilic polymer combined together.
What factors affect the shape of block copolymers produced?
Length of each part, temperature and concentration of NPs
What are the 5 ways one can direct self-assembly of block copolymers?
-Electric Fields
-Solvent Polarity
-Mechanical forces
-Chemical attachment to surfaces
-Epitaxial self-assembly on nano-patterned substrates
Give 4 applications of block copolymers
-Lithographic masks
-Scaffolds for biomaterials
-Porous membranes
-Templates for organising nanocrystals
Block copolymers can be stacked to form superlattices. Give and explain one example of a superlattice.
Triblock copolymer: hydroPHILIC - hydrophobic - hydroPHILIC parts
Right end of polymer rigid, and has well-defined length, so leads to well-ordered, crystalline structure
Other 2 parts are flexible and have varying length + composition, so disordered structure
Overall “mushroom-like” structure
How are ionically self-assembled monolayers formed?
+ve and -ve polymers self-assemble -> substrate (e.g. +ve) immersed in (e.g. -ve) polymer
Can build alternating layers of polymers as they will ionically attract.
Describe the synthesis process of ionically self-assembled monolayers.
Adsorption of polyanion, wash, adsorption of polycation, wash.
Continue sequence for more complex structures. -> can control thickness
Give 4 pros of DNA-based assembly
-v. specific
-reversible binding due to weak forces (e.g. can increase temp, give system energy, therefore bonds break)
-can make different structures
-provides different functionalities (by modifying w/ different functional groups)
Note: can make diff shapes through “Branched Junction Assembly” by programming complimentary strands or sections that will overlap. Can also fold DNA to make diff shapes.
Nanoparticle Assemblies Examples
See notes
