Huahua Huang

Synthesis of novel biobased polyimides derived from isomannide with good optical transparency, solubility and thermal stability

Novel biobased polyimides (PIs) with good optical transparency and comprehensive properties were synthesized from isomannide-derived diamine and dianhydride monomers. Three kinds of diamines including 2,5-diamino-2,5-dideoxy-1,4:3,6-dianhydroiditol (M1), 1,4:3,6-dianhydro-2,5-di-O-(4-aminophenyl)-D-mannitol (M2), and 1,4:3,6-dianhydro-2,5-di-O-(2-trifluoromethyl-4-aminophenyl)-D-mannitol (M3), as well as 1,4:3,6-dianhydro-2,5-di-O-(3,4-dicarboxyphenyl)-D-mannitol dianhydride (M4), were prepared based on isomannide. These diamines M1–M3 were reacted with M4 and a commercial dianhydride, 4,4′-oxydiphthalic anhydride (ODPA), via a two-step polymerization method, respectively, to yield a series of biobased PI films, PI-1 to PI-6. The resultant PIs had a high content of biomass up to 48 wt%, and they can be readily soluble in various non-proton polar solvents at room temperature. Most of the biobased PIs showed good optical transparency (transmittances at 450 nm over than 80%), along with a cut-off wavelength of 343–364 nm. Furthermore, due to the existence of rigid alicyclic isomannide among the polymeric backbone, biobased PIs maintained fairly high thermal stability with a glass transition temperature of 227–264 °C, and temperature at 5% weight loss over 400 °C in nitrogen. Meanwhile, these PIs exhibited outstanding mechanical properties with tensile strengths greater than 90 MPa and elongation at break higher than 6.0%. It was also found that the biobased PI series with alicyclic M1 possessed higher thermal stability than PIs with semi-aromatic diamines M2 and M3. Thereof, the introduction of biomass building blocks into PIs can offer a great opportunity to develop new sustainable materials with high performance for microelectronic and optoelectronic applications.

Mild halogenation of polyolefins using an N-haloamide reagent

Chlorinated polyolefins remain highly valued commodity polymers owing to their excellent physicochemical properties. The chief synthetic route to this variety of polymer involves the chlorination of polyolefin materials using chlorine gas, an extremely toxic and heavily monitored chemical. We hereby report the application of an N-chloroamide compound in the chlorination of both polyethylene (PE) and polypropylene (PP). An N-bromoamide reagent was also synthesized and used in the bromination of PE samples in an analogous fashion. Polyolefin halogenation reactions, including chlorination and bromination, were performed in solution with various feed ratios and the products were characterized by multi-instrumental analysis including proton nuclear magnetic resonance, size exclusion chromatography, differential scanning calorimetry, Fourier transform-infrared spectroscopy and thermogravimetric analysis. A peak halogen content of 32.7 and 31.9 wt% was determined for chlorine and bromine, respectively. Moreover, a high-density PE film was additionally chlorinated and the result was verified by X-ray photoelectron spectroscopy analysis. The new synthetic methodology has been confirmed to be a tunable and convenient alternative to the use of chlorine gas for the production of chlorinated polyethylene.

High performance polyimides with good solubility and optical transparency formed by the introduction of alkyl and naphthalene groups into diamine monomers

Three kinds of naphthalene-containing diamines with –H, –CH3 or –CH(CH3)2 substituents at the ortho-positions of the aniline ring including 4,4′-(naphthalen-1-ylmethylene)dianiline (BAN-1), 4,4′-(naphthalen-1-ylmethylene)bis(2,6-dimethylaniline) (BAN-2) and 4,4′-(naphthalen-1-ylmethylene)bis(2,6-diisopropylaniline) (BAN-3) were synthesized via a simple one-step electrophilic substitution reaction. These diamines were then reacted with three commercial dianhydrides, via chemical imidization under microwave irradiation, to obtain nine types of polyimide (PI). It was found that the introduction of alkyl side groups can improve the solubility and optical transparency of PIs. Moreover, compared with BAN-2 based PIs containing –CH3 groups, BAN-3 based PIs containing –CH(CH3)2 groups exhibited better solubility and optical transparency (transmittances at 450 nm of over 86%). Meanwhile, due to the presence of the rigid naphthalene side groups, all the PIs possessed high thermal stability with a glass transition temperature (Tg) of over 290 °C and a decomposition temperature at 5% weight loss of over 510 °C under nitrogen. Furthermore, the Tg of PI-2B composed of BAN-2 and 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) was found to be as high as 387 °C, which is comparable to that of the commercial and conventional PI material (Kapton®, Tg = 390 °C).