Monomeric and Dimeric Carboxylic Acid in Crystalline Cavities and Channels of Delta and Epsilon Forms of Syndiotactic Polystyrene

Abstract

Delta (δ) and epsilon (ε) co-crystalline forms of syndiotactic polystyrene with a carboxylic acid guest were obtained by sorption of liquid hexanoic acid in syndiotactic polystyrene films exhibiting delta and epsilon nanoporous-crystalline forms. The characterization study is facilitated by axially stretched syndiotactic polystyrene films, used both for polarized FTIR spectra and for WAXD fiber patterns. Particularly informative are two carbonyl-stretching FTIR peaks, attributed to monomeric and dimeric hexanoic acid. The dichroism of these carbonyl peaks indicates that both delta and epsilon phases are able to include hexanoic acid as isolated guest molecules, while only the epsilon phase is also able to include dimeric hexanoic acid molecules in its crystalline channels. The inclusion of both isolated and dimeric hexanoic acid species in the epsilon form crystalline channels produces extremely fast hexanoic acid uptakes by syndiotactic polystyrene epsilon form films.

Segregation of Benzoic Acid in Polymer Crystalline Cavities

“…Two recent papers by our group describe the CC phases of sPS with aliphatic carboxylic acids, showing that the crystalline channels of the ε form were able to host long carboxylic acids as well as dicarboxylic acids [ 17 , 18 ]. This selective and fast uptake of carboxylic acids in the crystalline channels of the sPS ε form is due to the formation of hydrogen bonded linear dimers and linear polymers for the monocarboxylic and dicarboxylic acid guests, respectively [ 17 , 18 ]. Moreover, the inclusion of hexanoic acid as an isolated guest of the crystalline cavities of the sPS δ form was also described [ 17 ].…”

“…This selective and fast uptake of carboxylic acids in the crystalline channels of the sPS ε form is due to the formation of hydrogen bonded linear dimers and linear polymers for the monocarboxylic and dicarboxylic acid guests, respectively [ 17 , 18 ]. Moreover, the inclusion of hexanoic acid as an isolated guest of the crystalline cavities of the sPS δ form was also described [ 17 ].…”

Thymol and Carvacrol: Phenolic Monoterpenes Extracted from the Essential Oil of Thymus vulgaris as Natural Antimicrobial Guests of Nanoporous Crystalline Syndiotactic Polystyrene Fibers

“…An useful tool to understand the host-guest interactions in a polymer matrix are polarized FTIR measurements. [62,63] Polarized FTIR analysis of axially oriented s-PS 𝛿-form films before and after immersion in carvacrol and in thymol/methyl acetate solution overnight at room temperature are shown in Figures 4 and 5, respectively. FTIR peaks located at 813, 858, 993, 1115, 1174, 1228, 1254 cm −1 related to carvacrol molecules [64] in s-PS film are apparent and, as shown, they are poorly dichroic (Figure 4, curve b).…”

“…The OH stretching region in FTIR spectra (3200-3600 cm −1 ) can be used to discriminate between guest molecules included into the crystalline phase and molecules dissolved in the amorphous phase. [39,62,[65][66][67][68][69] In particular, the peak located at 3532 or 3540 cm -1 is related to the OH groups of isolated guest molecules included in the crystalline phase while the broad band centered at ≈3400 cm -1 corresponds to molecules simply dissolved in the amorphous phase. The broadness of the OH stretching band is indeed due to hydrogen bonding between molecules.…”

Transparent and flexible high-surface area nanoporous crystalline PPO films

“…Two thermoplastic and commercially available polymers, poly-(2,6-dimethyl-1,4-phenylene)oxide (PPO) [1][2][3][4][5][6][7] and syndiotactic polystyrene (sPS), [7][8][9][10][11][12][13][14][15][16][17][18] can be easily co-crystallized with low molecular-mass guest molecules. Moreover, PPO [19][20][21][22][23][24][25][26] and sPS [27][28][29][30][31][32][33][34] presently are the only two polymers, whose co-crystalline forms can lead to nanoporous-crystalline (NC) forms after suitable guest removal procedures.…”