Exploring the difference in the topology−structure−conformation relationship for linear and cyclic graft polymers is an interesting topic. In this work, two libraries of linear graft (l-PPA-g-PS, with a linear backbone) and cyclic graft (c-PPAg-PS, with a cyclic backbone) polystyrenes with low ratios of the backbone-to-sidechain contour length (r c , from 1.26 to 6.22) and various grafting densities (σ, from 0.16 to 0.86) have been studied as models. Atomic force microscopy (AFM) characterization has indicated ellipsoidal and spherical morphologies for both l-PPA-g-PS and c-PPA-g-PS with no significant difference. By comparing the absolute (M w,abs ) and apparent (M w,app ) molar masses, it is found that M w,abs /M w,app varies from 1.5 to 3.5 and gradually increases with σ. By measuring g h 1/2 (g h 1/2 = R h,graft /R h,linear ), it is found that the two topologies have different compactness of conformation. By following the temperaturedependent interchain aggregation in cyclohexane, it is found that the cyclic backbone feature can suppress the interchain association and be more susceptible to graft density than linear graft polymers. The present study has clearly showed that the cyclic graft topology can potentially display unique structural and conformational properties, which can be attributed to the topological advantages such as more compact conformation and significant isotropic features.

Exploring an efficient way to purify the graft-onto polymerization products is an important but challenging problem. This work explores the feasibility of utilizing nanopore-based ultrafiltration for this purpose. First, a library of PPA Nd b -g-PS Nd g -σ graft-onto products with polystyrene (PS) sidechain and poly(propargyl acrylate) (PPA) backbone has been prepared, and the effect of molecular parameters, including contour length (l c ), sidechain radius (R sidechain ), and persistence length (l p ), on the flowassisted translocation and cutoff performance of PPA Nd b -g-PS Nd g -σ through nanopores with diameter D = 20 nm has been studied. At a low macroscopic flow rate Q = 0.2 mL/ h, it is found that for PPA Nd b -g-PS Nd g -σ chains with R sidechain > 1/2D, they are completely retained due to the size-sieving effect. More generally, it is found that the decrease of l c from ∼500 to ∼50 nm and R sidechain from 18.0 to 3.9 nm facilitates the diffusive passage of chains through nanopores; surprisingly, the increase of l p from 5.4 to 22.2 nm also facilitates the process, which actually signifies the possibility of enhanced chain orientation. At a high macroscopic flow rate Q > 0.2 mL/h, the increase in l c and R sidechain results in a larger critical macroscopic flow rate (Q c ) for chains to squeeze into the nanopores. When R sidechain > 1/2D, no l c -dependence is observed for the cutoff performance. Furthermore, it is found that the separation efficiency can be efficiently enhanced by increasing the solution concentration in the regime of C < C* with C* being the overlap concentration, which is demonstrated by one example of the practical purification process of the PPA 780 -g-PS 41 -60% model sample.

By using a model system composed of an anodic aluminum oxide nanopore (AAO), poly(benzyl acrylate) (PBA N ) adsorbent, and polystyrene (PS N ) probe, where N represents the degree of polymerization, this work has explored how the physical adsorption of PBA onto the surface of the AAO nanopore (r p ≈ 10 nm) influences the flow-driven translocation of PS in toluene. In the low flow rate range (Q = 0.02 mL/h), the translocation of PS chains is purely diffusive, and the partially reversible adsorption behavior of PBA N is observed only when N < ∼360, showing a strong chain length dependence. In the partially reversible regime, the interfacial thickness (δ) of the adsorption layer is estimated to be from ∼1.5 to ∼2.9 nm depending on the chain length. In the mixed solutions, when N increases from 0 to 75 and 150 for PBA N , the cut-off size (COS) of the membrane for broadly distributed PS B-285K (M w /M n ≈ 2.48) is estimated to decrease from ∼10.0 to ∼8.0 and ∼6.0 nm, respectively; in addition, the introduction of PBA 360 can promote the separation of narrowly distributed PS 655 and PS 1200 by regulating r e , whereas in the high flow rate range (Q > 0.02 mL/h), the translocation for PS long chains is based on the mechanism of molecular deformation, and the flow ratedependent translocation shows a strong dependence on the chain length of PBA N . Namely, in mixed solutions, when N increases from 150 to 360, the critical flow rate (Q c ) is found to slightly increase from ∼0.30 to ∼0.45 mL/h for PS 1500 translocation; in addition, the cut-off performance of PS B-285K displays dependence both on flow rate and PBA N chain length. Our result has demonstrated a novel strategy to regulate the cut-off performance during the translocation of (bio)macromolecules through nanopores via partially reversible interfacial physical adsorption.