Novel electrochromic polynorbornenes poly(NBPYTPAM) and poly(HNBPYTPAM), containing electroactive chromophores, were prepared via ring-opening metathesis polymerization (ROMP) from a new norbornene derivative (NBPYTPAM) using Grubbs’ catalyst and followed by hydrogen reduction. The glass transition temperatures (T g) of poly(NBPYTPAM) and hydrogenated poly(HNBPYTPAM) were 190 and 175 °C, respectively. The cyclic voltammogram of the poly(HNBPYTPAM) film cast onto flexible graphene-coated polyethylene terephthalene (PET) substrates exhibited two reversible oxidation redox couples at 1.0 and 1.9 V. Flexible electrochromic devices were fabricated from the electroactive polymers and graphene-coated PET substrates. The electrochromic characteristics of poly(HNBPYTPAM) showed excellent stability and reversibility, with multistaged color changes from its yellow neutral form to green and then to dark-blue.

Controlled grafting of polybetaine brushes onto hydrogen-terminated Si(100) substrates (Si-H substrates) was carried out via surface-initiated reversible addition-fragmentation chain-transfer (RAFT) polymerization. The azo initiator was immobilized on the Si-H surface through a threestep process: (i) coupling of an ω-unsaturated alkyl ester to the Si-H surface under UV irradiation, (ii) reduction of the alkyl ester into a hydroxyl group by LiAlH 4 , and (iii) esterification of the hydroxyl group with the initiator 4,4′-azo-bis(4-cyanopentanoic acid) after acid chlorination. In the presence of the chain-transfer agent, RAFT-mediated polymerization of the sulfobetaine monomer N,N′-dimethyl(methylmethacryloyl ethyl) ammonium propane sulfonate (DMAPS) was initiated from the surface-immobilized azo initiator to produce DMAPS polymer (PDMAPS) brushes on the silicon substrate (Si-g-PDMAPS). X-ray photoelectron spectroscopy (XPS) analysis indicated that the PDMAPS brushes had been successfully grafted onto the silicon surface. Atomic force microscopy (AFM) images revealed changes in the surface topography of the silicon substrates and the presence of polymer overlayers. Ellipsometry results indicated that the thickness of the polybetaine film increased linearly with the polymerization time. The "living" characteristics of the end functionality of the polybetaine brushes from the RAFT-mediated process was ascertained by block copolymerization with the anionic monomer sodium 4-styrene sulfonate (SS) to form the diblock polymer brushes (a Si-g-PDMAPS-b-PSS surface).

Compared with traditional thermosets, malleable thermosets have more applications in aerospace, biotechnology, and construction. Here we report a one-step, solvent-free, catalyst-free polycondensation method between diamine and formaldehyde to prepare a series of malleable hemiaminal dynamic covalent networks (HDCNs). The materials have excellent malleability and reprocessability by hot pressing. The Young's modulus and breaking strength of HDCNs obtained by the polycondensation of formaldehyde and 4,4-diaminodiphenylmethane (MDA) are as high as 1.6 GPa and 60 MPa, respectively, which can be facilely adjusted through the introduction of polyetheramine-400 (PEDA). Moreover, the HDCNs feature the shape memory ability with a recovery ratio above 93.5% and can be recycled by the addition of different monomers. This promising HDCN, prepared from economical raw materials, may have vast applications in industries.

Poly[N,N′-(1,4-phenylene)-3,3′4,4′-benzophenonetetracarboxylic amic acid] (PAmA) with grafted poly(methyl methacrylate) (PMMA) side chains (PAmA-g-PMMA) was synthesized via thermally induced graft copolymerization of methyl methacrylate (MMA) with ozone-pretreated PAmA in the reversible addition-fragmentation chain-transfer (RAFT)-mediated process. The graft copolymers were characterized by nuclear magnetic resonance (NMR), elemental analysis, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and molecular weight measurements. The "living" character of the grafted PMMA side chains was ascertained in the subsequent extension of the PMMA side chains. The nanoporous low dielectric constant (low-κ) polyimide (PI) films were obtained by thermal imidization of the PAmA-g-PMMA films in argon, followed by thermal decomposition of the PMMA side chains in air. The nanoporous PI films obtained from the RAFT-mediated PAmAg-PMMA had well-preserved PI backbones, porosity in the range of 5-20%, and pore size in the range of 5-15 nm. The pores were smaller, and the pore size distribution was more uniform than those of the corresponding nanoporous PI films obtained via graft copolymers from the conventional free radical process. Dielectric constants approaching 2.1 were obtained for the nanoporous PI film with a porosity of about 20%.

Comb-shaped copolymers consisting of rigid fluorinated polyimide (FPI) backbone and welldefined polystyrene (PS) side chains (FPI-cb-PS), or poly(pentafluorostyrene) (PFS) side chains (FPI-cb-PFS), were synthesized by atom transfer radical polymerization (ATRP) from the bromide-containing FPI macroinitiators (FPI-Br). The sizes of the FPI-Br macroinitiators (consisting of 14 repeat units in the rigid backbone) and cleaved PS and PFS brushes (consisting of 35-144 and 32-93 repeat units, respectively) were estimated from the gel permeation chromatography (GPC) results. The lengths of the PS and PFS side chains determined from 1 H NMR spectroscopy were comparable to those determined from GPC or theoretical analysis. X-ray photoelectron spectroscopy (XPS) results confirmed the presence of grafted PS and PFS side chains on the respective FPI-cb-PS and FPI-cb-PFS copolymers as well as the presence of one ATRP bromide initiator per FPI repeat unit in the FPI-Br macroinitiator. Orderly arrays of the comb-shaped macromolecules, consisting of rigid FPI rods (backbones) of 20-30 nm in length and flexible PS brushes (side chains) of 4-6 nm in width, were imaged by atomic force microscopy (AFM). In addition to having a dielectric constant (κ) as low as 2.1, the resulting comb-shaped FPI-cb-PFS copolymer also exhibited good solution processability and good thermal stability (up to 470 °C).