Block Copolymers

Block copolymers are a fascinating class of polymeric materials belonging to a bigfamily known as ‘‘soft materials.’’ This class of polymers is made by the covalentbonding of two or more polymeric chains that, in most cases, are thermodynamicallyincompatible giving rise to a rich variety of microstructures in bulk and insolution. The length scale of these microstructures is comparable to the size of theblock copolymers molecules (typically 5–50 nm); therefore, the microstructures arehighly coupled to the physical and chemical characteristics of the molecules. Thevariety of microstructures gives rise to materials with applications ranging fromthermoplastic elastomers and high-impact plastics to pressure-sensitive adhesives,additives, foams, etc. In addition, block copolymers are very strong candidates forpotential applications in advanced technologies such as information storage, drugdelivery, and photonic crystals.

AB type block copolymers

Four main synthetic routes have been developed (Figure 8.1) to prepare well-defineddiblock copolymers with narrow molecular weight distribution and very lowcompositional heterogeneity.

ABA

ABC

Graft copolymers

Target Structure: Linear densely grafted copolymer

Method: Functional monomer (protected), ATRP, Deprotection, Macroinitiator, ATRP

Chemistry

Polymer 45 (2004) 8173–8179

Macromolecules 2005, 38, 702-708

Grafting to reactions require the coupling of individual preformed tele-functional side chain precursors to a backbone polymer with distributed complementary functionality.

Grafting through consists of the polymerization of macromonomers.

Grafting from involves preparing the precursor to the backbone polymer with monomer units that contain functionalities ultimately capable of initiating polymerization of a second monomer.

Aim: Stimuli-responsive Bottle-brush Polymer Macromol. Rapid Commun. 2013Kejian Yao , Ying Chen , Jun Zhang , Clay Bunyard , Chuanbing Tang

Method

Chemistry

Ring opening metathesis polymerization (ROMP)

Synthesis of Block-Copolymer via Crossover-Chemistry in ROMP

Binder, Wolfgang Macromolecules 2009

Monofunctional Metathesis Polymers via Sacrificial Diblock Copolymers

Angew. Chem. Int. Ed. 2006, 45, 8045 –8048

“Perfect Comb” ADMET Graft Copolymers

Macromolecules 2001, 34, 6845-6849

Macrocyclization of Polymers via Ring-Closing Metathesis and Azide/Alkyne-‘‘Click’’-Reactions: Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 48, 671–680 (2010)