Abstract
In this paper, we present a tandem anionic-radical approach for synthesizing hypergrafted polymers. We prepared 4-(N,N-diphenylamino)methylstyrene (DPAMS) as a new radical-based inimer. Linear PDPAMS was prepared through anionic polymerization. Hypergrafted PDPAMS was synthesized through the self-condensing vinyl polymerization of DPAMS with linear PDPAMS. The linear backbone of PDPAMS, which incorporated latent radical initiating sites, served as a ‘hyperlinker’ to link hyperbranched side chains. The molecular weights of hypergrafted polymers increased as the length of the linear backbone chain increased. The hypergrafted structure of the resulting polymer was confirmed using a conventional gel permeation chromatograph apparatus equipped with a multiangle light scattering detector, nuclear magnetic resonance, differential scanning calorimetry, and thermogravimetric analysis. This strategy can be applied to synthesize other complex architectures based on hyperbranched polymers by changing the structure of a polymer backbone through anionic polymerization.
Highlights
Polymers with hyperbranched structures have gained increasing research interest for the preparation of polymer topologies with unique properties; potential areas of application include supramolecular assembly, drug delivery, and catalysis, etc. [1–9]
This strategy can be applied to synthesize other complex architectures based on hyperbranched polymers by changing the structure of a polymer backbone through anionic polymerization
A new radical-based inimer DPAMS was synthesized and the living controlled anionic polymerization of DPAMS was performed in THF at −78 °C using sec-BuLi as the initiator; Hyperbranched PDPAMS was synthesized through self-condensing vinyl polymerization (SCVP) of DPAMS; Hypergrafted PDPAMS was synthesized through SCVP of DPAMS in the presence of linear PDPAMS
Summary
Polymers with hyperbranched structures have gained increasing research interest for the preparation of polymer topologies with unique properties; potential areas of application include supramolecular assembly, drug delivery, and catalysis, etc. [1–9]. The process of controlling the molecular weight of hyperbranched polymer while keeping the large number of terminal functional groups is a noteworthy challenge To address this problem, we intend to graft hyperbranched polymers onto a linear backbone through tandem anionic polymerization and SCVP of a radical-inimer, which produce a hypergrafted polymer. Anionic polymerization is well-established as the best methodology for the synthesis of homopolymers, copolymers, and end-functionalized polymers with controlled polymer chain lengths and narrow molecular weight distributions [31–34]. The obtained polymers contained pendants of radical initiators, which were used to graft hyperbranched polymers obtained by SCVP of inimers to linear backbones The mechanism of this approach is shown in Scheme 1. The goals of this work were to synthesize hypergrafted polymers with different molecular weights by controlling linear backbones, and to remain the number of terminal functional groups unchanged. Thermal crosslinkage of pendent N-benzyl-N-phenylaniline groups was observed in thermogravimetric analysis, resulting in multistep decomposition and a remaining weight of approximately 8–15 wt % at 700 °C
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