Organocatalyzed ring-opening polymerization (ROP) of ?-caprolactone (CL) and 4,4'-bioxepanyl-7,7'-dione as bis-lactone cross-linker was carried out within the high internal phase oil-in-oil emulsions (HIPEs) at 50 °C. In this way, the cross-linked poly(?-caprolactone) (PCL) polyHIPE foams with ~85% porosity were synthesized. The thermomechanical properties of the prepared polyHIPEs were studied and found to be strongly dependent on the degree of PCL cross-linking. The melting and crystallization temperatures as well as the degree of crystallinity of PCL polyHIPE foams decrease with increasing degree of cross-linking. Semi-crystalline polyHIPEs demonstrate shape memory behavior with excellent shape fixity and shape recovery. At an appropriate degree of PCL cross-linking, the temporary shape of polyHIPE can be fixed at room temperature, while a transition to the permanent shape occurs when heated to 40 °C. Moreover, a two-way shape memory behavior of the PCL polyHIPEs was observed under constant stress. The developed synthetic method has opened up the possibilities for the preparation of advanced porous materials based on biodegradable and bicompatable polymers such as synthetic polypeptides (Polymer Chemistry 2020, 11, 4260).
COBISS.SI-ID: 6748442
In this paper, we report on the synthesis of semi-interpenetrating polymer networks (semi-IPNs), which served us as the precursors for the preparation of porous polystyrene (PS) monoliths. Semi-IPNs were prepared in situ by simultaneous orthogonal polymerizations, where linear poly(?-caprolactone) (PCL) was synthesized by organocatalyzed ROP of ?-caprolactone (CL) and poly(styrene-co-divinylbenzene) (PS) network by a free-radical polymerization of styrene/divinylbenzene. To obtain porous PS monoliths, PCL domains were selectively removed by hydrolysis under basic conditions. By changing the amount of organocatalyst for ROP of CL, the relative polymerization kinetics of both monomers was varied, which was found to have a profound effect on the morphology of thus-obtained PS frameworks. This work demonstrates the importance of the kinetics of simultaneous and orthogonal polymerizations, as it governs the time order of system gelation and phase separation, which in turn strongly dictates the morphology of the PS monoliths. This work demonstrates extensive experience of the group on the synthesis of PS-monoliths, which are also applicable for the purification of biological vaccines. In March 2020, we asked for a partial adaptation of the program, as based on this work we were contacted by the company BIASeparations for a joint collaboration in the development of PS-monolith columns for mRNA purification.
COBISS.SI-ID: 6560026
The achievement describes a hierarchically structured porous carbon nanocomposite by a simple emulsion templated synthesis, which contains microporous zeolite nanocrystals embedded in the macroporous skeleton. The combination of zeolite nanocrystals embedded in the walls of carbon foam results in such unique structural properties that provide excellent ability to selectively sequester CO2. The synergism of zeolites and carbon foam results in an adsorbent with significantly enhanced CO2 capture capacity (5 mmol•g-1), exceptional selectivity and reusability under humid conditions (more than 70% efficiency after 30 regeneration cycles). Even more impressively, the electrically conductive carbon skeleton enables rapid and energy-efficient regeneration of the adsorbent by exploiting the Joule effect, in which the heat required to regenerate the adsorbent is generated by passing a low-voltage electrical current through an electrically conductive carbon skeleton. Thus, the energy consumption for the regeneration of the adsorbent by direct heating with electric current is estimated to be only about 12 kWh, which is more than 1000x less than currently comparable adsorbent regeneration technologies for CO2 capture. Za to delo smo prejeli nagrado ARRS Odlični v znanosti 2020 na področju interdisciplinarnih raziskav.
COBISS.SI-ID: 22970134
We report on a simple and efficient chemical recycling process for aliphatic polyamides (PA66, PA1010, PA11, PA12), whereby PAs are converted exclusively into their constituent monomers even in the presence of reinforcement additives, such as carbon- and glass-fibers. In this process, the rate of PA hydrolysis reaction, performed under microwave irradiation in the presence of HCl as an acid catalyst, depends on the PA type, HCl/amide mole ratio, and type and amount of reinforcement additives. PA66 is completely converted into the constituent monomers at 200 °C and 1.25 HCl/amide mole ratio in 10 min. Long-chain PAs (PA11, PA12, and PA1010) and PAs containing glass- or carbon-fiber reinforcement additives need at the same experimental conditions longer reaction times. Alternatively, they can be completely hydrolyzed at 200 °C within a comparable reaction time at higher HCl/amide mole ratio of 2.5. Complete and straightforward conversion of PAs into the constituent monomers in the absence of side reactions simplifies the isolation and purification of monomers and reinforcement additives, which have been recovered in high yields and quality comparable to that of commercially available chemicals. The article was also highlighted in ChemViews Magazine, as it offers a possible solution for recycling of aliphatic polyamides and thus reducing the impact of plastic waste on the environment (https://www.chemistryviews.org/details/news/11273753/Microwave-Assisted_Chemical_Recycling_of_Polyamides.html).
COBISS.SI-ID: 35255043
Cellulose nanocrystals (CNCs) were surface modified with 3-isocyanatopropyl triethoxysilane (ICPTS) in tetrahydrofuran at 62-63 °C using triethylamine as a catalyst. ICPTS modified CNCs were studied as a nanofiller in nanocomposites with linear low-density poly(ethylene) (LLDPE) prepared by melt processing. Compared to unmodified CNCs, the ICPTS modified CNCs show enhanced compatibility with LLDPE as shown by SEM. Nanocomposites molded at 120 °C showed a 20% increase in Young’s modulus and 30% increase in tensile strength compared to neat LLDPE. The degree of LLDPE crystallinity is beside the CNC reinforcing network formation an important decisive factor in defining the final mechanical properties of LLDPE/CNC nanocomposites. The maximal enhancement of mechanical properties was observed at rather low amount of added ICPTS modified CNCs (1-2 wt.%), which is important for practical application. By modification of CNCs with ICPTS, the CNCs polarity is reduced resulting in their improved compatibility with LLDPE matrix.
COBISS.SI-ID: 14253059