The preparation of well-controlled poly(N-cyclohexyl-exo-norbornene-5,6-dicarboximide) polymers

Abstract

We have studied the ring-opening metathesis polymerization of N-cyclohexyl-exo-norbornene-5,6-dicarboximide using the following 4 initiators: Grubbs 1, Grubbs 2, Hoveyda-Grubbs 1 (HG1) and Hoveyda-Grubbs 2 (HG2). Only the Grubbs 1 initiator was able to precisely control the polymer molecular weight. Polymerizations initiated by the HG1, Grubbs 2 and HG2 initiators could not be controlled well. Both the Grubbs 1 and HG1 yielded polymers with a high trans % (85-98%), whereas Grubbs 2 and HG2 yielded polymers with a lower trans % (50-52%). The level of molecular weight control for the four initiators decreased in the order Grubbs 14HG14HG24Grubbs 2. We also demonstrated that, in the case of polymers produced using Grubbs 1, the refractive indices (RIs) of the polymers decreased in a linear and controllable fashion from 1.539 to 1.534 at 633 nm, as the molecular weight was increased from 6700 to 26 400. This change represented a decrease in the RI of 0.005. INTRODUCTIONThe academic interest in poly(N-exo-norbornene-5,6-dicarboximide) (poly(NDI)) polymers has recently increased substantially, and its applications span physics, 1 chemistry 2 and biology. 3 A small selection of these interesting applications include cell adhesion materials, membranes, insulating materials and various optics applications. [4][5][6][7][8][9] This breadth of applications can be attributed to the fact that, as a polymer class, poly(NDI)s have been demonstrated to exhibit favorable thermal and mechanical properties, which greatly extend their range of practical applications. 10-14 Furthermore, ring-opening metathesis polymerization allows the preparation of well-defined random, block and alternating copolymers that extend the utility of poly(NDI)s as a system to prepare reactive and functional polymers. 15,16 Therefore, a systematic study of the influence of the Grubbs initiator on the precise controllability of the molecular weight and stereochemistry of a standard NDI monomer is of practical utility. Monomer preparation for poly(NDI)s is simple and easy. 17 Tlenkopatchev and coworkers have studied poly(NDI)s in detail using the Grubbs 1 (G1) and Grubbs 2 (G2) initiators. 13,14,18,19 Such initiators are known to impart trans-cis conformations into the polymer backbone. In this study, we focused on the monomer N-cyclohexyl-exo-norbornene-5,6-dicarboximide (CyNDI (4)) (Scheme 1). This monomer and polymer are soluble in common organic solvents such as chloroform and tetrahydrofuran. Furthermore, the monomer CyNDI (4) is easy to prepare in large quantities. Currently, the four different initiators G1, G2, Hoveyda-Grubbs 1

Catalytic Synthesis of Secondary Amine-Containing Polymers: Variable Hydrogen Bonding for Tunable Rheological Properties

“…For P1 GPC gave an average M n of 25 800 (113 repeat units) and a dispersity ( Đ ) of 1.07. MALDI-TOF mass spectrometry was consistent with the monomer repeat unit as well as the anticipated phenyl and methylene end groups − (see Figures S2 and S3).…”

Living ring‐opening metathesis polymerization of norbornenes bay‐functionalized perylene diimides

“…However, the polymerization of M1 using HG2 displayed cis and trans ratio of 23:77 (Figures S11 and S12). In general, G3 or HG2 initiated ROMP of norbornenes produce a mixture of isomeric olefinic isomers, 41,29 however in our case the polymerization of M1 displayed slightly higher ratios of trans olefin content (~67–77%) compared with the literature counterparts (~50–52%), the trans content of olefins part usually predominating in the polymer chain 42,43 …”

“…The crude mixture of the brominated 2a and 2b is virtually insoluble in any organic solvent, thus separation of the regioisomers were carried out at the next stage. Imidization of the mixture of 2a and 2b with octyldecylamine in N‐methyl‐2‐pyrrolidone (NMP) with 5% vol/vol of AcOH 39–42 afforded a mixture of 1,7‐ and 1,6‐dibrominated versions of perylene diimides 3a and 3b in 74% yield in a ratio of 5:1 (Scheme 1A).…”

User Guide to Ring-Opening Metathesis Polymerization of endo-Norbornene Monomers with Chelated Initiators

“…However, literature examples conventionally use exo -norbornene monomers − for ROMP owing to their reduced steric encumbrance and concomitantly increased reactivity and polymerization control relative to their endo-counterparts. − Although reports on ROMP of endo -norbornene monomers exist, − the utility of stable chelated initiators in combination with these less reactive, yet more accessible endo -derivatives has not been systematically examined. The reduced accessibility of exo -norbornene imide monomers arises in part from the requisite endo -to- exo isomerization for norbornene-anhydride that is both energy (∼180 to 250 °C) and time/material intensive (up to 16 h reaction time and as many as six recrystallizations from benzene with <20% overall yield). ,− From an applied perspective, endo -norbornene imide polymers have been observed to possess higher glass transition temperatures relative to their exo -analogues, a likely consequence of increased segmental packing and energetic barriers to backbone rotation while retaining comparable thermal stability and mechanical performance. , Thus, a rapid and controlled polymerization strategy for endo -norbornene monomers using a tunable and stable metathesis initiator would be of significant utility to the polymer science community.…”