Polystyrene (PS) is one of the ubiquitous polymeric materials in our daily life. It contains countless amount of π-π interactions caused by benzene rings on PS. Due to the interaction, PS is brittle. To deal with the issue, involving soft phase such as rubber or weak additional interactions have been reported. Cyclodextrin (CD) is one representative macrocyclic molecule exhibiting host-guest interaction. CD can contain proper guest molecules in its cavity to form inclusion complexes. As this process is reversible, the process results in various functions, for example toughness. Simply adding acetylate β or γ cyclodextrin (AcβCD or AcγCD) to PS enhanced mechanical properties of PS (Figure (a) and (b)). In particular, only 3~4 wt% of acetylate CD (AcCD) increased the fracture energy of PS by 4 times (Figure (c)). The PS composites with AcβCD kept Young’s moduli regardless of the amount of the AcβCD. On the other hand, AcγCD increased Young’s moduli and the fracture energy at the same time. Polymethylmethacrylate (PMMA), which has no moiety to interact with AcCD, was not toughened. Adding CD decreased the fracture energy of the PMMA composites with the increase in Young’s moduli. AcCD in PS forms domains composed of PS and AcCD both. Host-guest interaction occurs at the interfaces between the domains and PS matrix. Benzene rings on PS are recognized by AcCD on the interfaces when prepared. The recognized benzene rings move out from the AcCD during deformation and other benzene rings form the host-guest interaction with the free AcCD. Consequently, PS is toughened without no decrease in any mechanical properties. This simple addition expands the range of application of the host-guest interaction of CD.

Reinforcing polystyrene through host-guest interaction with addition of acetylated cyclodextrin

ACS Spring Meeting 2021

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