Dendrons and Dendritic Terpolymers: Synthesis, Characterization and Self-Assembly Comparison

Abstract

To the best of our knowledge, this is the very first time that a thorough study of the synthetic procedures, molecular and thermal characterization, followed by structure/properties relationship for symmetric and non-symmetric second generation (2-G) dendritic terpolymers is reported. Actually, the synthesis of the non-symmetric materials is reported for the first time in the literature. Anionic polymerization enables the synthesis of well-defined polymers that, despite the architecture complexity, absolute control over the average molecular weight, as well as block composition, is achieved. The dendritic type macromolecular architecture affects the microphase separation, because different morphologies are obtained, which do not exhibit long range order, and various defects or dislocations are evident attributed to the increased number of junction points of the final material despite the satisfactory thermal annealing at temperatures above the highest glass transition temperature of all blocks. For comparison reasons, the initial dendrons (miktoarm star terpolymer precursors) which are connected to each other in order to synthesize the final dendritic terpolymers are characterized in solution and in bulk and their self-assembly is also studied. A major conclusion is that specific structures are adopted which depend on the type of the core connection between the ligand and the active sites of the dendrons.

Synthesis, Characterization and Structure Properties of Biobased Hybrid Copolymers Consisting of Polydiene and Polypeptide Segments

“…In Figure 3, 1 H-NMR spectra for the four synthesized samples are presented, indicating the different chemical shifts due to the various polydiene conformations, which is in accordance with the results obtained from the IR spectroscopy. The characteristic chemical shifts in the monomeric unit of both PB and PI have already been thoroughly reported in the literature and are in good agreement with the results presented in this study [44,45]. The -NH-groups in the main polypeptide chain are usually evident at 7.5 ppm [3,14], but due to the overlapping of the shift attributed to the deuterated solvent (CDCl 3 ), a precise calculation of the contributing protons is not possible.…”

“…TGA thermographs of all the synthesized hybrid materials.The glass transition temperatures (T g s) of the components, as well as the potential mixing between the chemically dissimilar blocks, were identified from DSC experiments. In the samples PI 3,4/1,2 -b-P(o-Bn-L-Tyr) and PB 1,2 -b-P(o-Bn-L-Tyr), the T g s are expected at temperatures equal to −30 • for the PI 3,4 (~55-60%) segment while for PB 1,2 at approximately 0 • C, as already thoroughly reported in the literature[44,45,49,50]. The remaining polydienes, namely PI 1,4 (in PI 1,4 -b-P(o-Bn-L-Tyr)) and PB 1,4 )in PB 1,4 -b-P(o-Bn-L-Tyr)) display lower T g s, at approximately −70 • and −90 • , respectively [51-53].In Figure6, the DSC thermographs corresponding to the second heating of all four different samples are presented.…”

“…The -NH-groups in the main polypeptide chain are usually evident at 7.5 ppm [3,14], but due to the overlapping of the shift attributed to the deuterated solvent (CDCl3), a precise calculation of the contributing protons is not possible. Specifically, for the case of PI 1,4 -b-P(o-Bn-L-Tyr), the PI microstructure consisting of 90% PI 1,4 and 10% PI 3,4 , two distinctive peaks are evident at 839 cm −1 and 890 cm −1 (redcolor spectrum), respectively, whereas in the case of PI 3,4/1,2 -b-P(o-Bn-L-Tyr), the absence of the 1,4 microstructure indicated that the reaction took place in a polar environment leading to 3,4/1,2 microstructures predominantly (blue-color spectrum) [44,45]. Coherent results were also acquired for the PB segment both in the case of nonpolar PB 1,4 -b-P(o-Bn-L-Tyr) and polar PB 1,2 -b-P(o-Bn-L-Tyr) depicted in green-and purple-color spectra in Figure 2, respectively.…”

“…For P(o-Bn-L-Tyr), the Tgs were approximately evaluated at 60 °C and 53 °C, respectively. For the PB1,4-b-P(o-Bn-L-Tyr), the existence of two additional Tgs (−27 °C and 3 °C) was attributed to the mixing of the components and the presence of vinyl poly(butadiene) (PB1,2~10%), which is obtained after polymerization in a nonpolar environment under anionic polymerization conditions and high-vacuum techniques [44,45]. In Figure 6, the DSC thermographs corresponding to the second heating of all four different samples are presented.…”

Quo Vadis Carbanionic Polymerization?

“…Avgeropoulos’ group reported the synthesis and self-assembly of various types of well-defined miktoarm star polymers and dendrimers consisting of PS and immiscible polydiene blocks or PDMS via anionic polymerization high-vacuum techniques and appropriate chlorosilane chemistry. − On the other hand, other groups developed new multifunctional initiators for the anionic polymerization of styrene and dienes generating star homo/copolymers. , These DPE-based new initiators were soluble in hydrocarbon solvents and did not require polar additives during the polymerization …”