Synthesis and characterization of polycyanurate networks modified by oligo(ϵ‐caprolactone) as precursors of porous thermosets

Abstract

Oligo(e-caprolactone)-modified polycyanurate networks were synthesized by thermal polycyclotrimerization of dicyanate ester of bisphenol E in the presence of a dihydroxy-telechelic poly(e-caprolactone) (PCL) oligomer with varying compositions. Using FTIR, gel fraction content and density measurements, it has been proved that the main part of the reactive modifier was chemically incorporated into the PCN network structure. According to the thermal behavior of the polymer networks as investigated by TGA, they can be divided into two groups. The first group of systems with low modifier content (i.e., up to 20 wt %) is characterized by one stage of decomposition under nitrogen, and two stages under oxygen. A second group of systems with higher modifier content is generally characterized by two stages of decomposition in nitrogen and three stages in oxygen. DSC and DMTA investigations have shown the occurrence of at least a two-phase structure in all the samples. The PCN/PCL-based hybrid networks can be effectively used as precursors for the generation of porous PCN thermosets, as evidenced by FTIR and SEM.

Thermostable Nanoporous Polycyanurates

“…DSC investigation the situation found for pure PCN. Such a broadening of T g is consistent with the noticeable extent of structural heterogeneity in the PCN/PCL networks, as previously evidenced by dynamic mechanical thermal analysis (DMTA) [25]. After partial hydrolysis of the PCL fragments from PCN/PCL hybrid networks, the T g, onset dramatically increased and ΔT g narrowed, due to the removal of substantial amounts of PCL.…”

“…In fact, the aforementioned reactive modifiers were partly chemically incorporated into the network structure through the condensation reaction of their terminal hyd roxyl or urethane groups with cyanate (-O-C≡N) functions of the growing PCN network. In our previous work [25], we have investigated the structure and properties of PCN/PCL hybrid networks derived from DCBE and a dihyd roxy-telechelic oligomer of PCL. Fig.…”

“…Nevertheless, the absence of the absorption band at 1293 cm -1 arising from C-O and C-C stretching vibrations of PCL crystallites [27,28], revealed that PCL fragments did not crystallize within the PCN network. In these systems, PCL sub-chains are either covalently incorporated within the PCN network or constrained within the matrix (free PCL oligomers), preventing any PCL crystallization [25].…”

“…In this context, we have undertaken a thorough investigation of the scope and limitations associated with the use of miscellaneous PCN systems for the design of (meso)porous crosslinked film materials. One of our groups has reported several works on the modification of PCNs with telechelic thermoplastic poly mers [18][19][20][21][22][23][24], and we have recently broadened this family of modified PCN networks through the synthesis and characterization of the PCN/PCL systems [25]. Herein, we propose an alternative route to porous PCN networks without using high temperatures, where hybrid networks can be effectively employed as precursors.…”

Synthesis, morphology, and thermal stability of nanoporous cyanate ester resins obtained upon controlled monomer conversion

“…During the synthesis of PCL-modified CER films, partial incorporation of the reactive modifier into CER crosslinked structures was found through condensation reactions of terminal hydroxyl groups from PCL with cyanate groups of growing CER networks [12].…”