Thermal Transitions of ε Crystalline Phases of Syndiotactic Polystyrene

Polymerization of Aniline in Tubular Cavities of the Crystalline Phase of Syndiotactic Polystyrene: Proposal of a Preparation Method of Sophisticated Polymer Composites

Syndiotactic polystyrene (SPS) has a unique crystalline phase, named ε, that has a tubular cavity inside. We connected these cavities by optimizing the solvent used to process the films and to polymerize aniline within these channeling cavities only by immersing the films in degassed hydrochloric acid solutions of ammonium persulfate. We succeeded in fixing pentameric to octameric oligoaniline in the cavities of the SPS ε crystalline phase. This is a new and sophisticated preparation method of polymer composites between SPS and linear oligomers/polymers within its long-connected tubular cavities.

Enantiomeric guests with the same signs of chiral optical responses

The chiral response of non-racemic molecules, being guests of s-PS co-crystalline films, does not depend on their R or S molecular chirality but essentially only on the polymer host supramolecular chirality.

Crystalline complex of syndiotactic polystyrene with poly(ethylene glycol) dimethyl ethers

It has been clarified that syndiotactic polystyrene (sPS) forms co-crystalline structures with polyethylene glycol dimethyl ethers (PEGDMEs) with molecular weights ranging from 178 to 1,000 g·mol(-1) through a guest exchange procedure assisted by a plasticizing agent. The PEGDME molecules are incorporated into the spaces between sPS polymer sheets consisting of (T(2)G(2))(2) helices. The results of X-ray diffraction and gravimetric measurements suggest that one or less molecules are included per unit cell for PEGDME with average molecular weight of 1,000 g·mol(-1), which indicates the possibility that longer polymeric molecules can be introduced into sPS lattices with multiple site occupation.

Molecular sensing by nanoporous crystalline polymers

Chemical sensors are generally based on the integration of suitable sensitive layers and transducing mechanisms. Although inorganic porous materials can be effective, there is significant interest in the use of polymeric materials because of their easy fabrication process, lower costs and mechanical flexibility. However, porous polymeric absorbents are generally amorphous and hence present poor molecular selectivity and undesired changes of mechanical properties as a consequence of large analyte uptake. In this contribution the structure, properties and some possible applications of sensing polymeric films based on nanoporous crystalline phases, which exhibit all identical nanopores, will be reviewed. The main advantages of crystalline nanoporous polymeric materials with respect to their amorphous counterparts are, besides a higher selectivity, the ability to maintain their physical state as well as geometry, even after large guest uptake (up to 10-15 wt%), and the possibility to control guest diffusivity by controlling the orientation of the host polymeric crystalline phase. The final section of the review also describes the ability of suitable polymeric films to act as chirality sensors, i.e., to sense and memorize the presence of non-racemic volatile organic compounds.