Self-Assembly of Copolymers
“Self-assembled block copolymer thin films have attracted a great deal of attention recently as templates for nanolithography. A diblock copolymer contains two immiscible polymer chains covalently bonded together and, on annealing, undergoes a microphase separation to form self-assembled periodic nanoscale domains. The domains can exist in various morphologies depending on the volume fractions of the two constituents of the polymer, including spheres, cylinders, and lamellae. The domain size and period scale with the molecular weight, making these materials useful masks for nanofabrication. Thin films of block copolymers have been used to pattern semiconductor dot and antidot arrays metal dots and nanowires, magnetic storage media and devices, such as capacitors, memory cells, and transistors have been fabricated using block copolymer lithography “
“Successful implementation of block copolymer (BCP) patterning depends on the ability to control the morphology, orientation, and packing of the domains. Block copolymer domain patterns typically have good short-range order but lack long-range order. Long-range ordering has been accomplished by various approaches such as the application of external electrical fields temperature gradients shear fields or by using chemically or topographically patterned substrates.”
“Most studies using patterned substrates have focused on the behavior of a monolayer of spherical or in-plane cylindrical block copolymer domains, or on short cylinders or lamellae oriented perpendicular to the surface. In addition, block copolymers have been confined within certain geometries such as pores or droplets which introduce additional boundary conditions and can promote block copolymer morphologies not found in the bulk, such as the formation of concentric cylinders by lamellar block copolymers, or helical structures by cylindrical block copolymers.”
(Chuang and Ross, US Patent 7.790,045, 9/7/2010)
Fabrication
Microfabrication
Photo-Ordering of Copolymers
Polyurethane (PUR) Copolymers
Self-Assembly
Self-Assembly of Polyelectrolyte Copolymers
Self-Assembly with Click Chemistry
Recent US Patents
11/30/2010|
7,842,337
Method of nano-patterning block copolymers and method of manufacturing polarizer and color filter using the same
Kim et al of Samsung, South Korea have developed a polarizer based on nanopatterns of block copolymers. This is done by coating block copolymers on a substrate and aligning self-assembled block copolymers in a direction of the thickness gradient by heat-treating the block copolymers. (RDC 4/19/2011)\
9/7/2010
7,790,045
Formation of close-packed sphere arrays in V-shaped grooves
Chuang and Ross of MIT were able to form well ordered face centered cubic arrays of block copolymers using V shaped grooves on a surface. A toluene solution of polystyrene (PS)-block-polyferrocenyldimethylsilane (PFS) block copolymer was spin coated on the grooved substrates and annealed under vacuum for 72 hours. The copolymer spheres are deposited within the grooves with the (111) FCC planes parallel to the walls of the groove and the (100) FCC planes parallel to the substrate surface. (RDC 11/28/2010)
Recent Journal Articles
Tuning nanoscopic self-assembly of diblock copolymer blends on a two-dimensional interface
( 136–143)Journal of Polymer Science B: Polymer Physics 49, #2 (2011)
Spreading amphiphilic diblock copolymers on a two-dimensional liquid interface has been observed to produce nanoscale features via self-assembly. Lu et al developed a model based on polymer entanglement and surface diffusion to predict the size of the structures. Characteristic nanoscopic dimensions can be tuned by adjusting two easily controllable macroscopic quantities: the blend composition and the initial surface concentration. (RDC 12/21/2010)
Microstructure and morphology of self-assembling multiblock poly(ethylene-1-butene)-ncopolymers in solution studied by wide-Qsmall-angle neutron scattering and microscopy
( 144–158)Journal of Polymer Science B: Polymer Physics 49, #2 (2011)
Radulescu et al showed that decreasing the temperature formation and evolution of multisized structural levels showed a hierarchical organization on the length scale from 1 nm up to 10 μm. One-dimensional polymer aggregates arising as initial structures associate and branch that lead to the occurrence of complex macroaggregates with diffusive interfaces and sizes of several microns. The one-dimensional copolymer structure shows longitudinal density modulation and micellar-like substructures in neat polymer solutions. When wax is added, this structure becomes more homogeneous in decrease of temperature as a consequence of the cocrystallization of wax and copolymer. (RDC 12/21/2010)
Targeting of Cancer Cells Using Quantum Dot–Polypeptide Hybrid Assemblies That Function as Molecular Imaging Agents and Carrier Systems
(4091–4097)Advanced Functional Materials 20 #23 (2010)
Atmaja et al of Stanford University, California formed the assemblies self-assembly of carboxyl-functionalized quantum dots and poly(diethylene glycol-L-lysine)-poly(L-lysine) diblock copolypeptide molecules, and they are modified with peptide ligands containing a cyclic arginine-glycine-aspartate [c(RGD)] motif that has affinity for αvβ3 and αvβ5 integrins overexpressed on the tumor vasculature. Binding to U87MG glioblastoma cells can be modulated and optimized by changing either the conditions under which the assemblies are formed or the relative lengths of the different blocks in the