Over the past few years, the concurrent (1) development of polymer synthesis and (2) introduction of new mathematical models for polymer dynamics have evolved the classical framework for polymer dynamics once established by Doi–Edwards/de Gennes. Although the analysis of supramolecular polymer dynamics based on linear rheology has improved a lot recently, there are a large number of insecurities behind the conclusions, which originate from the complexity of these novel systems. The interdependent effect of supramolecular entities (stickers) and chain dynamics can be overwhelming depending on the type and location of stickers as well as the architecture and chemistry of polymers. This Perspective illustrates these parameters and strives to determine what is still missing and has to be improved in the future works.

Supramolecular polymers bearing weak hydrogen bonds (sticker) can express outstanding dynamic properties due to their labile association. Studying the linear viscoelasticity (LVE) of this type of polymer can provide us with sufficient knowledge to design polymeric materials for applications that need dynamic properties such as self-healing. Using different compositions of flexible weak stickers, LVE analysis showed scalings corresponding to a transition from a linear precursor to a cluster. By introducing one sticker per repeating unit of the precursor polymer, the effect of sticker distribution along the chain as well as phase separation is excluded. However, even a fully functionalized polymer could not show any network formation, whereas surprisingly, a stable cluster was formed. This proves that weakly associated networks do not dissociate rapidly and can relax as a cluster at extended time before the dissociation of stickers can lead to the relaxation of linear analogous (slow kinetics similar to strong physical or even chemical bonds.) On the other hand, the absence of a gel even in fully sticker-functionalized polymers shows that the weakness of these polymers can be described as their weakness in complete association (thermodynamically not favored).

A series of poly(tetrahydrofuran)s with molecular weights above entanglement molecular weight Me were synthesized, and one of their end-groups was functionalized with a supramolecular entity so that the corresponding polymers form a brushlike structure suitable for comparison with conventional irreversible bottlebrush polymers. To compare their relaxation mechanisms, linear rheology was employed and showed that a hierarchical relaxation, which is usually observed in bottlebrush polymers, occurs in these materials, too. The polymer chain segments close to the supramolecular backbone are highly immobilized due to strong association in the center of polymer brush and cannot relax via reptation mechanism, which is mainly responsible for linear entangled polymer relaxations. Therefore, disentanglement can take much longer through contour length fluctuations and arm retraction processes similar to covalent bottlebrush polymers and combs. The relaxed ends of polymers then act as solvent to let the remaining segments of the polymeric brush undergo Rouse-like motions (constraint release Rouse). At longer times, additional plateau appears, which can be attributed to the relaxation of the entire supramolecular bottlebrush polymer via hopping or reptative motions. With an increase of temperature, viscoelastic solid behavior turns into viscoelastic liquid due to reversible depolymerization of the supramolecular backbone of the bottlebrush polymer. The elastic modulus (G′ in the order of kPa) was much less than the values found for the entanglement plateau modulus of linear poly(tetrahydrofuran) (in order of MPa). This low modulus value, which exists up to very low frequencies (high temperatures), makes them a good candidate for supersoft elastomers.

Aromatic moieties containing oligoesters and polyesters synthesized by enzymatic and conventional polymerizations of AB-type alkylenehydroxybenzoates.

No abstract

Supramolecular polymer combs/brushes can be used as smart materials which incorporate the properties of linear polymers with branch polymers depending on the temperature, grafting density, branch molecular weight and most importantly type of non-covalent interaction between the main chain and side chains. Three sets of polymers were synthesized and mixed based on a specific interaction between the main chain and the side chain polymers. The first two sets based on the combination of 2,4-diamino-1,3,5-triazine (DAT) : thymine (THY) and 2-ureido-4[1H]-pyrimidinone (UPy) : (1-(6-isocyanatohexyl)-3-(7oxo-7,8-dihydro-1,8-naphthyridin-2-yl)urea) (ODIN) were a blend and the third one using ODIN : ODIN interactions was used without a main chain. The polymer set using ODIN : ODIN interaction showed long-range ordering due to strong ODIN aggregation, whereas UPy : ODIN-based polymer combs showed comb-like clusters without any ordering. The phase separation in the THY : DAT system was more pronounced and was further improved after the addition of more equivalents of side chains. Moreover, using melt rheology, consistent with the SAXS data, it was concluded that long-range ordering is responsible for the elastic properties and the flow temperature (T flow ) is lower than the order-disorder transition temperature (T ODT ). This work can be considered as a toolkit for the design of bottlebrush and comb polymers as well as supersoft elastomers and stimuli-responsive materials. † Electronic supplementary information (ESI) available. See

The origin of unique rheological response in supramolecular brush polymers is investigated using different polymer chemistries (poly­(methyl acrylate) (PmA) and poly­(ethylene glycol) (PEG)), topologies (linear or star), and molecular weights. A recently developed hydrogen-bonding moiety (1-(6-isocyanatohexyl)-3-(7-oxo-7,8-dihydro-1,8-naphthyridin-2-yl)-urea) (ODIN) was coupled to PmAs and PEGs to form supramolecular brush polymers, the backbone of which is formed by the associated moieties. At low molecular weights of monofunctionalized polymers (both PmA and PEG), the formed brushes are mostly composed of a thick backbone (with very short arms) and are surrounded by other similar brush polymers, which prevent them from diffusing and relaxing. Therefore, the monofunctionalized PmA with a low M n does not show terminal flow even at the highest experimentally studied temperature (or at longest time scales). By increasing the length of the chains, supramolecular brushes with longer arms are obtained. Due to their lower density of thick backbones, these last ones have more space to move and their relaxation is therefore enhanced. In this work, we show that despite similarities between covalent and transient brush polymers, the elastic response in the latter does not originate from the brush entanglements with a large M e (entanglement molecular weight), but it rather stems from the impenetrable rigid backbone and caging effect similar to the one described for hyperstars.

There is a major push by governments and value chain partners to move towards circular options for difficult-to-recycle post-consumer products such as waste mattresses.[1] In the Netherlands alone ~1.5 million mattresses are discarded yearly, of which majority (>60%) is incinerated.[2] A sustainable solution to recycle waste mattresses is required to enable the Dutch industry meet the circular economy goals set by the Dutch government.[3] This paper shares major findings from the screening level life cycle assessment (LCA) of four End-of-Life (EoL) options for post-consumer mattresses: landfill, incineration with energy recovery, pyrolysis and mechanical recycling using powdering. The LCA was an important work package of a technology development project with the objective to quantify potential sustainability benefits of the pyrolysis of waste mattresses.[4] The emphasis of the pyrolysis process is on product recovery as chemical feedstock. The study showed that pyrolysis is a better option than incineration in terms of greenhouse gases ( GHG) and cumulative energy demand (CED) for all the studied cases. Base case analysis showed that pyrolysis of waste mattresses can save approximately 526 kg CO2-eq. and approximately 5.1 GJ (24% savings) CED per ton waste mattresses compared to incineration. Finally, the study concluded that mechanical recycling can either be better or worse than pyrolysis depending on the processes and quality of recycled material.