Nanoconfinement Induced Direct Formation of Form I and III Crystals inside in Situ Formed Poly(butene-1) Nanofibrils

We show that under relevant processing conditions, isotactic poly­(butene-1) (iPB-1) directly crystallizes into the thermodynamically stable form I and III from the melt state when it is confined in nanocylinder shape domains. The iPB-1 nanofibers with an average diameter of about 200 nm confined in an incompatible polyethylene (PE) matrix show the kinetically favored form II in addition to form I. However, only form I and III are present when the average size of nanofibers is further reduced to about 60 nm after localization of organoclay nanoparticles at the interface of the iPB-1 nanofibers and PE matrix. Even though the materials were brought to temperatures higher than the melting temperature of iPB-1, the formation of unstable form II is completely suppressed by the nanoconfinement of the iPB-1 phase. It is believed that the nanoconfinement reduces the mobility of iPB-1 chains and consequently alters the kinetics of form II crystallization. The localization of organoclay at the interface completely further suppresses the formation of form II crystal by enhancing the confinement effect.