Light Scattering Study of Internal Motions of Ultralong Comb-like Chains in Dilute Solutions under Good Solvent Conditions

Abstract

Internal dynamics of polymer chains is one of the most important fundamental problems in polymer physics. This work reports the first example of a dynamic light scattering (DLS) study of internal motions of well-defined ultralong comb-like chains in dilute solutions under good solvent conditions. Using two well-characterized comb-like model samples with controlled parameters and narrow distributions (M w /M n ≈ 1.30 and M w ≈ 10 7 g/mol), the asymptotic behavior of the reduced first cumulant [Γ* = Γ(q)/(q 3 k B T/ η 0 )], the number of relaxation modes in Γ(q) distribution curves, the characteristic relaxation time (τ 1 ) of the first internal mode, and the q-dependent relative strength of internal motions have been experimentally quantified and carefully analyzed where q is the scattering vector. Specifically, the DLS results reveal the following: (i) Γ*(q ≫ 1), that is, the value of Γ* at the very high q regime, is not sensitive to structural details (local rigidity and side chain length); (ii) similar to hyperbranched polymers, the asymptotic power law in the regime of 3.0 < (q⟨R g ⟩) < 5.5 is also found to be a better indicator, which could reflect the structural details for comb-like polymers; (iii) the comparison of experimentally determined and theoretically calculated values of τ 1 shows that the classical theory of linear chains could still satisfactorily describe the intrachain relaxation behavior of comb-like chains; and (iv) the side-chain grafting-induced rigidity could result in an enhanced separation of translational and internal motions but simultaneously result in a significant suppression of the strength of overall internal motions. The present study not only reveals that the modes of internal motions of a given system are mainly determined by the relaxation of the main contour of a given chain structure rather than the local chain rigidity but also provides useful experimental data for further theoretical modeling of internal dynamics of various topological polymers.

Study of Linear and Cyclic Graft Polystyrenes with Identical Backbone Contour in Dilute Solutions: Preparation, Characterization, and Conformational Properties

“…As shown in Figure , the average sizes are found to increase with the grafting density but irrelevant with the chain topology. For both l -PPA- g -PS 23 and c -PPA- g -PS 23 , ellipsoidal and spherical morphologies are observed, which is different from our previously observed wormlike chain morphology for l -PPA 19000 - g -PS 13 with an ultralarge DP of the backbone . In addition, the morphology of cyclic graft polymers is also different from that reported by Schappacher and Deffieux .…”

“…The modifications of linear and cyclic backbones with propargyl bromide were conducted with a tetramethylguanidine promoted esterification approach according to the literature, which furnished the alkyne-functional l -PPA and c -PPA, respectively. − As shown in Figure a, the SEC curves of l -PPA and c -PPA still show the difference in M p,c / M p,l , which is found to be around 0.80 (Table ), similar to that for P t BA samples. In addition, the observed characteristic peak “h” in Figure b, attributed to the proton signal from the alkyne group, also indicates the success of esterification.…”

“…For both l-PPA-g-PS 23 and c-PPA-g-PS 23 , ellipsoidal and spherical morphologies are observed, which is different from our previously observed wormlike chain morphology for l-PPA 19000 -g-PS 13 with an ultralarge DP of the backbone. 46 In addition, the morphology of cyclic graft polymers is also different from that reported by Schappacher and Deffieux. 47 In their work, the DP range of the backbone is 550−950, which is at least 3 times of our sample.…”

Molecular Dynamics Simulations of Self-Healing Topological Copolymers with a Comblike Structure

“…Comblike polymers have an intrinsic ability toward forming ordered structures, and understanding the structure of comb polymers is a pre-requisite to controlling their performance. There are also some reports on the regulation of mechanical properties by tuning the structural parameters of comblike macromolecules. − Urban et al have demonstrated that simple comb polymers based on methyl methacrylate and n -butyl acrylate show repeatable self-healing properties, which rely on van der Waals interactions and have significant implications for the fabrication of low-cost self-healing polymers and coatings. The present study focuses on coarse-grained MD (CGMD) simulations of alternating comblike molecules with a goal to fundamentally probe the influence of different kinds of architectural parameters on the mechanical and self-healing properties of such materials.…”

Conformational, crystalline and rheological properties of poly(octadecyl-co-methyl acrylate) statistically random copolymers

“…Polymer Chemistry different from our previously observed wormlike chain morphology for PPA 19000 -g-PS 13 with an ultralarge DP of the backbone. 24 In the sample preparation process before the AFM measurements, the dilute polymer solution shows a strong concentration during the solvent evaporation process and the alkane side chain itself is crystalline, so we believe that the chain dynamics can affect the conformational state, aggregation state, and the resulting morphology.…”