Orthogonal maleimide and thiol deprotections were combined with thiol-maleimide coupling to synthesize discrete oligomers/macromolecules on a gram scale with molecular weights up to 27.4 kDa (128mer, 7.9 g) using an iterative exponential growth strategy with a degree of polymerization (DP) of 2 -1. Using the same chemistry, a "readable" sequence-defined oligomer and a discrete cyclic topology were also created. Furthermore, uniform dendrons were fabricated using sequential growth (DP=2 -1) or double exponential dendrimer growth approaches (DP=22n -1) with significantly accelerated growth rates. A versatile, efficient, and metal-free method for construction of discrete oligomers with tailored structures and a high growth rate would greatly facilitate research into the structure-property relationships of sophisticated polymeric materials.

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Orthogonal maleimide and thiol deprotections were combined with thiol-maleimide coupling to synthesizediscrete oligomers/macromolecules on ag ram scale with molecular weights up to 27.4 kDa (128mer,7 .9 g) using an iterative exponential growth strategy with ad egree of polymerization (DP) of 2 n À1. Using the same chemistry,a"readable" sequence-defined oligomer and ad iscrete cyclic topology were also created. Furthermore,u niform dendrons were fabricated using sequential growth (DP = 2 n À1) or double exponential dendrimer growth approaches (DP = 2 2 n À1) with significantly accelerated growth rates.Aversatile,efficient, and metal-free method for construction of discrete oligomers with tailored structures and ah igh growth rate would greatly facilitate researchi nto the structure-property relationships of sophisticated polymeric materials.Itiswell-documented that the property/function of polymers strongly relies on molecular weight (MW), topology and sequence distribution. [1] Nature creates av ariety of biopolymers,s uch as DNA [2] and proteins, [3] with precisely defined chain lengths,f unctional sequences,a nd topologies.S ince most artificial polymers are polydisperse with various chemical structures and MWs at the molecular level, the research on structure-property relationship is mainly limited to ambiguous or statistical evaluation methods. [4] Therefore,i t is of great interest for the synthesis of discrete oligomers with uniform chain lengths (that is,am onodisperse MW), monomer unit sequences,a nd topologies,t oa dvance more comprehensive and accurate study of the structure-property relationships of polymers. [5] Driven by this challenge,chemists have made numerous efforts to synthesize discrete oligomers utilizing diverse approaches.Within these pioneering works, [6] iterative sequential, [7] or exponential [8] growth through terminal deprotections/transformations and end-to-end couplings, [9] is commonly used for preparation of discrete oligomers.W henb uilding discrete oligomers,t he efficient orthogonal chain terminal deprotections,t ogether with endto-end coupling reaction, are highly desirable for ah igh degree of polymerization (DP) and scalable preparation. A number of coupling reactions,s uch as Suzuki coupling, [8b] Sonogashira, [9a] Stille, [9b] Buchwald, [8e] Wittig, [9c] copper catalyzed azide-alkyne cycloaddition (CuAAC), [8d, i, k, l] and Glaser coupling reactions, [10] as well as esterification, [11] amidation, [9d] and etherification, [8c, 9e] have been utilized in precision synthesis of oligomers.A mong them, metal-catalyzed coupling reactions are frequently used owing to their versatility, effectiveness,a nd sometimes "click-like" manner. [7g, 8d, i, k] However,m etal ions may accumulate after many cycles and thereby contaminate target products.This circumstance might yield inaccurate measurements when investigating the structure-property relationships of the discrete oligomerslimiting their potential for future applications.Herein, for the first time,wecombined orthogo...

Poly(butylene adipate-co-terephthalate) (PBAT) biocomposites containing carbon nanotubes (CNTs) were prepared by melt compounding. The linear viscoelasticity of composites, including creep, creep recovery and stress relaxation in the solid state, and dynamic shear flow in the molten state, were studied and then further described by the viscoelastic models, aiming at exploring relaxation of hierarchical structures of CNTs and obtaining structural parameters of CNTs in PBAT matrix. The results reveal that CNTs are dispersed mainly as flocs or small aggregates in PBAT, which is further confirmed by the structural parameters of CNTs obtained through model simulations on the dynamic rheological responses of composites. The presence of CNTs retards overall kinetics of creep and stress relaxation of PBAT. This is attributed to highly restrained viscoelastic and viscoplastic deformation of PBAT chain coils, rather than slightly confined elastic deformation of chain segments because the chain coils is in the same size-scale with the CNT flocs.