In this work we present a combined analysis of small-angle neutron scattering, linear rheology and pulsed field gradient nuclear magnetic resonance spectroscopy experiments on the supramolecular association and chain structure of well-defined telechelically modified poly(ethylene glycol) (PEG) in the bulk. Oligomeric PEG was functionalized with directed heterocomplementary hydrogen-bonding end-groups, thymine (Thy) and diaminotriazine (DAT). The polarity of the backbone polymer is comparable to the end groups and avoids clustering of the groups basing on energetic arguments. Their linear association behavior in the ideal melt state was investigated on the microscopic/molecular level as a function of temperature. By means of a selective labeling scheme, which should ideally lead to the formation of alternating hydrogeneous-deuterated building block sequences if the hydrogen bonding reaction is exclusively heterocomplementary, we showed that the Thy–DAT association is dominant and a Thy–Thy homoassociation is approximately three times less probable. Latter nondirected association gives rise to a considerable amount of random-copolymerization without affecting seriously neither the macroscopic melt viscosity nor the diffusivity of the supramolecular associates. From the q-dependence of a multiblock RPA structure factor, the linear association in the melt is confirmed. Furthermore, this diffusion and viscosity study reveals simple Rouse dynamics of supramolecular polymer chains with molecular weight much larger than the entanglement mass M e. The Rouse-like dynamics of long supramolecular chains indicates short lifetime hydrogen bonds of the end groups. Our results are in excellent agreement with the related polycondensation theory.
Calix[4]pyrrole–chloride interactions are affected not only by the choice of countercation in halogenated solvents, but show a specific dependence on the way in which these cations are bound within the electron rich, bowl‐like calix[4]pyrrole cavity formed upon chloride anion complexation. In dichloromethane, the affinities of simple meso‐octamethylcalix[4]pyrrole (1) for methyl‐, ethyl‐, and n‐butylammonium chlorides are on the order of 105, 104, and 102 M−1, respectively, as determined from isothermal titration calorimetry (ITC) analyses. These cation‐dependent anion affinity effects, while clearly evident, are less pronounced in other halogenated solvents, such as 1,2‐dichloroethane. Support for the proposed cation complexation selectivity is provided by solid state X‐ray crystallographic analyses.
The chain and association dynamics of supramolecular polymer ensembles decisively determines their properties. Using neutron spin echo (NSE) spectroscopy we present molecular insight into the space and time evolution of this dynamics. Studying a well characterized ensemble of linearly associating telechelic poly(ethylene glycol) melts carrying triple H-bonding end groups, we show that H-bond breaking significantly impacts the mode spectrum of the associates. The breaking affects the mode contributions and not the relaxation times as was assumed previously. NSE spectra directly reveal the so far intangible H-bond lifetimes in the supramolecular melt and demonstrate that for both the microscopic and the macroscopic dynamics of the supramolecular ensemble the instantaneous average of the M_{w} distribution governs the system response at least as long as the Rouse picture applies.
We present a small angle neutron scattering (SANS) study of the association of heterocomplementary telechelic polypropylene glycol (PPG) polymers, bearing either diaminotriazine (DAT) or thymine (Thy) stickers as end-groups, both in the melt and in dilute solution. The SANS data are critically examined for the architecture and morphology as well as relative extent of linear assembly in the apolar solvent toluene. A random phase approximation (RPA) approach, adapted for a supramolecularly assembled multiblock copolymer is presented, which allows to extract the interaction parameters between the constituents and the medium. From the proposed approach, which describes very well heterocomplementary hydrogen-bonding telechelic polymers in both diluted toluene solution and in the melt, we conclude that linear association prevails.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.