In this paper, ring closure click chemistry methods have been used to produce cyclic c-PLLA and c-PDLA of a number average molecular weight close to 10 kg/mol. The effects of stereochemistry of the polymer chains and their topology on their structure, nucleation and crystallization were studied in detail employing Wide Angle X-ray Scattering (WAXS), Small Angle X-ray Scattering (SAXS), Polarized Light Optical Microscopy (PLOM) and standard and advanced Differential Scanning Calorimetry (DSC). The crystal structures of linear and cyclic PLAs are identical to each other and no differences in superstructural morphology could be detected. Cyclic PLA chains are able to nucleate much faster and to produce a higher number of nuclei in comparison to linear analogues, either upon cooling from the melt or upon heating from the glassy state. In the samples prepared in this work, a small fraction of linear or higher molecular weight cycles was detected (according to SEC analyses). The presence of such "impurities" retards spherulitic growth rates of c-PLAs making them nearly the same as those of l-PLAs. On the other hand, the overall crystallization rate determined by DSC was much larger for c-PLAs, as a consequence of the enhanced nucleation that occurs in cyclic chains. The equilibrium melting temperatures of cyclic chains were determined and found to be 5 ºC higher in comparison with values for l-PLAs. This result is a consequence of the lower entropy of cyclic chains in the melt. Self-nucleation studies demonstrated that c-PLAs have a shorter crystalline memory than linear analogues, as a result of their lower entanglement density. Successive selfnucleation and annealing (SSA) experiments reveal the remarkable ability of cyclic molecules to thicken, even to the point of crystallization with extended collapsed ring conformations. In general terms, stereochemistry had less influence on the results obtained in comparison with the dominating effect of chain topology.

Since the time first synthetic macrocycles were observed as academic curiosities, great advances have been made. Thanks to the development of controlled polymerization processes, new catalytic systems and characterization techniques during the last decades, well-defined cyclic polymers are now readily accessible. This further permits the determination of their unique set of properties, mainly due to their lack of chain ends, and their use for industrial applications can now be foreshadowed. This review aims to give an overview on the recent progresses in the field of ring polymers to this day. The current state of the art of the preparation of cyclic polymers, the challenges related to it such as the purification of the samples and the scalability of the synthetic processes, the properties arising from the cyclic topology and the potential use of cyclobased polymers for biomedical applications are as many topics covered in this review.

One of the main issues when using traveling wave ion mobility spectrometry (TWIMS) for the determination of collisional cross-section (CCS) concerns the need for a robust calibration procedure built from referent ions of known CCS. Here, we implement synthetic polymer ions as CCS calibrants in positive ion mode. Based on their intrinsic polydispersities, polymers offer in a single sample the opportunity to generate, upon electrospray ionization, numerous ions covering a broad mass range and a large CCS window for different charge states at a time. In addition, the key advantage of polymer ions as CCS calibrants lies in the robustness of their gas-phase structure with respect to the instrumental conditions, making them less prone to collisional-induced unfolding (CIU) than protein ions. In this paper, we present a CCS calibration procedure using sodium cationized polylactide and polyethylene glycol, PLA and PEG, as calibrants with reference CCS determined on a home-made drift tube. Our calibration procedure is further validated by testing the polymer calibration to determine CCS of numerous different ions for which CCS are reported in the literature. Graphical Abstract ᅟ.

Several families of polymers possessing various end-groups are characterized by ion mobility mass spectrometry (IMMS). A significant contribution of the end-groups to the ion collision cross section (CCS) is observed, although their role is neglected in current fitting models described in literature. Comparing polymers prepared from different synthetic procedures might thus, be misleading with the current theoretical treatments. We show that this issue is alleviated by comparing the CCS of various polymer ions (polyesters and polyethers) as a function of the number of atoms in the macroion instead of the usual representation involving the degree of polymerization. Finally, we extract the atom number density from the spectra which gives us the possibility to evaluate the compaction of polymer ions, and by extension to discern isomeric polymers.

The synthesis of symmetric cyclo poly(ε-caprolactone)-block-poly(l(d)-lactide) (c(PCL-b-PL(D)LA)) by combining ring-opening polymerization of ε-caprolactone and lactides and subsequent click chemistry reaction of the linear precursors containing antagonist functionalities is presented. The two blocks can sequentially crystallize and self-assemble into double crystalline spherulitic superstructures. The cyclic chain topology significantly affects both the nucleation and the crystallization of each constituent, as gathered from a comparison of the behavior of linear precursors and cyclic block copolymers. The stereochemistry of the PLA block does not have a significant effect on the nonisothermal crystallization of both linear and cyclo PCL-b-PDLA and PCL-b-PLLA copolymers.

Rationale Since their discovery, cyclic polymers have attracted great interest because of their unique properties. Today, the preparation of these macrocyclic structures still remains a challenge for polymer chemists, and most of the preparation pathways lead to an inescapable contamination by linear by‐products. As the properties of the polymers are closely related to their structure, it is of prime importance to be able to assess the architectural purity of a sample. Methods In this work, the suitability of ion mobility spectrometry‐mass spectrometry (IMS‐MS) for the quantification of two isomers was investigated. A cyclic poly(L‐lactide) was prepared through photodimerization of its linear homologue. Since IMS‐MS can be used to differentiate cyclic polymer ions from their linear analogues because of their more compact three‐dimensional conformation, the present work envisaged the use of IMS‐MS for the quantification of residual linear polymers within the cyclic polymer sample. Results Using the standard addition method to plot calibration curves, the fraction of linear contaminants in the sample was determined. By doing so, unrealistically high values of contamination were measured. Conclusions These results were explained by an ionization efficiency issue. This work underlines some intrinsic limitations when using IMS‐MS in the context of the relative quantification of isomers having different ionization efficiencies. Nevertheless, the linear‐to‐cyclic ratio can be roughly estimated by this method.

This work reports on the preparation of highly pure cyclo-polylactides (M n ≈ 4 000 g · mol -1 ) by the optimization of the copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction applied on α-azide-ω-alkyne linear polylactide (PLA) precursors. By adjusting parameters such as the rate of reactant addition and the catalyst loading, monocyclic PLA's with a degree of purity of 93 % are obtained in few minutes. Highly pure monocycles (purity as high as 99.9 %) are also possibly prepared in few hours. Otrzymywanie cyklopolilaktydów o wysokiej czystości poprzez optymalizację katalizowanej miedzią cykloaddycji azydek-alkinStreszczenie: Opisano optymalizację syntezy cyklopolilaktydów w katalizowanej miedzią(I) reakcji cykloaddycji azydku do alkinu (CuAAC), której celem było uzyskanie polimerów o wysokiej czystości i średnim ciężarze cząsteczkowym M n ≈ 4 000 g · mol -1 . Do reakcji użyto prekursorów, którymi były liniowe α-azydo-ω-alkinowe polilaktydy (PLA). Dobrano warunki syntezy, takie jak szybkość dodawania reagenta oraz ilość używanego katalizatora, które pozwalają na otrzymanie w ciągu kilku minut monocyklicznego PLA o stopniu czystości 93%. Prowadząc syntezę w ciągu kilku godzin można otrzymać monocykliczny polimer o czystości do 99,9%.Słowa kluczowe: laktyd, polimeryzacja z otwarciem pierścienia, cykloaddycja azydek-alkin katalizowana miedzią, cyklizacja.Due to intriguing characteristics issued from their endless topology, cyclic structures have been the subject

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