Poly(N‐isopropylacrylamide) (PNIPAM) is an important thermo‐responsive polymer that finds applications in many areas. However, the preparation of PNIPAM‐based block copolymer nanoparticles with higher‐order morphologies at high solids is challenging. Herein, aqueous photoinitiated polymerization‐induced self‐assembly (photo‐PISA) of N‐isopropylacrylamide (NIPAM) using an asymmetrical cross‐linker is developed for one‐step preparation of PNIPAM‐based block copolymer nanoparticles with various morphologies (spheres, worms, and vesicles). It is demonstrated that reaction temperature has a great effect on both polymerization kinetics and morphologies of block copolymer nanoparticles. Reversible addition‐fragmentation chain transfer (RAFT) reactive groups embedded inside the PNIPAM core provide a landscape for further functionalization. PNIPAM‐based block copolymer nanoparticles with different surface properties are prepared by seeded photo‐PISA at room temperature. Finally, these block copolymer nanoparticles are also used as additives to tune mechanical properties of hydrogels via covalent cross‐linking.

One-dimensional block copolymer micelles have exhibited considerable promise in various fields. However, the large-scale preparation of one-dimensional block copolymer micelles is always challenging. Here, we report the preparation of cylindrical block copolymer micelles up to 30% w/w solids by photoinitiated reversible addition-fragmentation chain transfer (RAFT) dispersion polymerization of 2-(perfluorooctyl)ethyl methacrylate (FMA) in ethanol. Because of the liquid-crystalline ordering effect of the PFMA core-forming block at low temperatures, cylindrical micelles could be obtained over a wide range of degree of polymerization of PFMA. The length of cylindrical micelles could be roughly controlled by changing the molar mass of the macromolecular chain transfer agent (macro-CTA). Finally, the concept of seeded growth was successfully incorporated into photoinitiated RAFT dispersion polymerization, allowing the epitaxial growth of cylindrical micelles from seeds. We expect that this method will offer considerable opportunities for the large-scale preparation of well-defined cylindrical micelles that may find applications in some specific areas.