Koopolymers

Koopolymers are a class of block copolymers that combine two or more distinct polymer segments within a single macromolecule. The term is derived from the German word "Koop" meaning "cooperative," reflecting the cooperative interactions among the segments that give rise to unique material properties. A typical koopolymer consists of a hydrophilic block, such as poly(ethylene glycol), attached to a hydrophobic block, such as poly(styrene), linked through a flexible spacer. The molecular architecture can be linear, branched, or star-shaped, and the stoichiometric ratio of the blocks is precisely controlled during synthesis.

Koopolymers are usually prepared by controlled radical polymerization techniques such as atom transfer radical polymerization (ATRP) or reversible addition‑fragmentation chain‑transfer polymerization (RAFT). These methods allow for narrow dispersity and well‑defined end‑groups, enabling subsequent block extensions or functionalization. The resulting macromolecules self‑assemble in selective solvents, forming micelles, vesicles, or lamellar structures, depending on the block lengths and solvent polarity.

The cooperative nature of their segmental interactions leads to responsive behavior. For example, koopolymers incorporating stimuli‑responsive monomers can change their morphology in response to pH, temperature, or ionic strength. Applications are therefore focused on drug delivery, where the micelle core can encapsulate hydrophobic drugs while the hydrophilic shell confers circulation stability. Other uses include surface coatings that combine anti‑fouling with antimicrobial activity, and as templates for nanolithography. Current research also explores integrating conductive or magnetic blocks, opening possibilities in flexible electronics and biomedical sensors.