Nematic-to-Isotropic Phase Transition in Poly(L-Lactide) with Addition of Cyclodextrin during Abiotic Degradation Study

Abstract

Poly(L-lactide) is capable of self-assembly into a nematic mesophase under the influence of temperature and mechanical stresses. Therefore, subsequent poly(L-lactide) films were obtained and characterized, showing nematic liquid crystal properties both before and after degradation. Herein, we present that, by introducing β-cyclodextrin into the polymer matrix, it is possible to obtain a chiral nematic mesophase during pressing, regardless of temperature and time. The obtained poly(L-lactide) films exhibiting liquid crystal properties were subjected to degradation tests and the influence of degradation on these properties was determined. Thermotropic phase behavior was investigated using polarized optical microscopy, X-ray diffraction, and differential scanning calorimetry. The degradation process demonstrated an influence on the liquid crystal properties of pressed polymer films. The colored planar texture of the chiral nematic mesophase, which was not observed prior to degradation in films without the addition of β-cyclodextrin, appeared after incubation in water as a result of the entrapment of degradation products in the polymer matrix. These unusual tailor-made properties, obtained in liquid crystals in (bio)degradable polymers using a simple method, demonstrate the potential for advanced photonic applications.

Poly(l-Lactide) Liquid Crystals with Tailor-Made Properties Toward a Specific Nematic Mesophase Texture

“…First, a PLLA rigid film was heated from RT to a temperature below its T m = 149.9 °C (from 20 to 110 °C, see Table ) under the pressure of the press jaws to 5 tons for about 1 to 5 min, and then the PLLA was cooled to a temperature below the T g = 54.3 °C (i.e., RT), releasing the pressure of the jaws. Additionally, the chiral nematic mesophase was obtained by appropriate control of the temperature, heating time, and pressure force, as well as by adding a fine powder, for example, talc (also peptides or cyclodextrins; publications in preparation , ). When the sample was cooled to RT, the polymer retained the structure of the nematic mesophase. , Slow plastic deformation, which is the pressing of the polymer in the temperature range between T g and T m , facilitates ordering, as the straightening (orientation) of the chains takes place during the deformation.…”

Specific Condis Crystal-like Mesophase of Poly(butylene succinate-co-butylene adipate)

“…Cast PBSA thin films were heated from RT to the temperature below the T m = 92.1 °C and subsequently cooled to RT (i.e., above its T g = −43.4 °C). Several different temperatures of RT, 40, 60, 80, 90, and 100 °C were selected due to the experience from previous results, indicating that the mesophase usually takes place slightly above the T g . , For the experiment, the pressure of the press jaws, 2, 2.5, and 5 t, and the time from 1 to 5 min were also selected. It is assumed that when the specimen is cooled to RT, the polymer is expected to retain the structure of the condensed crystal mesophase.…”

Preparation and characterization of amphiphilic, biodegradable, waterborne polyurethanes without using organic solvent and catalyst

“…1,2 In addition, due to the increase in plastic waste year by year, degradable polymers have become attractive for environmental applications. 3,4 Polyurethane (PU) is one of the polymeric materials most widely used in coatings, inks, adhesives, and foams, due to its excellent combination of properties, such as chemical resistance, exibility, and mechanical and adhesive properties. [5][6][7] However, several organic solvents, including toluene, xylene, formaldehyde, etc., are used in PU synthesis, which seriously pollute the environment and endanger human health.…”

“…1,2 In addition, due to the increase in plastic waste year by year, degradable polymers have become attractive for environmental applications. 3,4…”