Formation of polymeric nanoparticles via Bergman cyclization mediated intramolecular chain collapse

Abstract

Polymeric nanoparticles were synthesized through Bergman cyclization mediated intramolecular chain collapse. Enediyne moieties were incorporated into linear polymers through copolymerization or post-polymerization modification. The resulted enediyne containing copolymers were then subjected to intramolecular chain collapse under ultra-dilute condition or applying a continuous addition technique. The occurrence of Bergman cyclization was confirmed with IR, NMR and DSC analysis. The intramolecular chain collapse was characterized with GPC, DSC, and AFM. Dramatic decreases of apparent molecular weights of linear copolymers were observed after Bergman cyclization. The structural diversity of enediyne precursors and mild chain collapse condition allow wide monomer selection, which facilitates preparation of a broad range of polymeric nanoparticles. Low-k dielectric thin films were prepared using polymeric nanoparticles through “porogen” approach. The packing tightness of polymeric nanoparticles showed strong influence on film formation behavior with MSSQ matrix. With tightly packed polymeric nanoparticles as sacrificial pore generators, thin films with dielectric constants of as low as 2.1 were obtained.