Modeling Branched Polyethylene:  Copolymers Possessing Precisely Placed Ethyl Branches

Abstract

A structural investigation of precise ethylene/1-butene (EB) copolymers has been completed using step polymerization chemistry. The synthetic methodology needed to generate four model copolymers is described; their primary and higher level structure is characterized. The copolymers possess an ethyl branch on every 9th, 15th, and 21st carbon along the backbone of linear polyethylene. Melting points and heats of fusion decrease with increased branch frequency. Differential scanning calorimetry and infrared spectroscopy show highly disordered crystal structures favoring ethyl branch inclusion. On the other hand, the EB copolymers contain high concentrations of kink and gauche defects independent of branch frequency. These model copolymers are compared with random copolymers produced using traditional chain chemistry and previously synthesized ADMET EP copolymers.

Probing the Effects of Hydrophilic Branch Size, Distribution, and Connectivity in Amphiphilic Polyethylene

“…Grubbs' first generation catalyst was a gift from Materia, Inc. Diene alcohols 1a,b and 2a,b, and oligoethoxy-p-tosylates were synthesized according to the literature. [5,22,23] Anhydrous DMF (40 mL) was cannula transferred into an ovendried, three-neck round-bottom flask equipped with a magnetic stirrer and gas inlet, and was charged with 2 equiv. of sodium hydride (60% dispersion in mineral oil).…”

“…Monomers 3a-d and 4a-d were prepared via Williamson etherification of primary and secondary diene alcohols 1a,b and 2a,b (prepared as previously reported) [5,22] with oligoethoxy-p-tosylates. [23] The use of the primary diene alcohol places a carbon atom directly off the backbone of the resulting polymer; throughout this report the monomers and polymers produced in this fashion will be described as ''primary.''…”

Acyclic Diene Metathesis with a Monomer from Renewable Resources: Control of Molecular Weight and One‐Step Preparation of Block Copolymers

“…[3,4] The observation that the introduction of a N-heterocyclic carbene (NHC) to the catalyst leads to metathesis initiators with improved activity [5][6][7] as well as stability led to the development of the second-generation catalysts from Grubbs [8,9] and Hoveyda [10] that are widely applied today in organic synthesis as well as polymer chemistry. [1,[11][12][13][14] Therefore, the ADMET polymerization technique has not only led to the preparation of well-defined, branched polyolefins (from branched monomers) that would not be accessible by other methods [15,16] but has also opened ways to prepare polyolefins with a number of different functional groups. [17][18][19][20][21] Even if the preparation of a large variety of different polymers is possible through ADMET polymerization as discussed above, relatively little is known about the use of ADMET polymerizations for the preparation of telechelics or even block copolymers.…”

Acyclic Triene Metathesis Polymerization with Chain‐Stoppers: Molecular Weight Control in the Synthesis of Branched Polymers

“…Acyclic diene metathesis (ADMET) polymerization is a versatile technique for the preparation of a variety of linear polymers, [1,2] polymers with a defined degree of branching, [3,4] telechelics [5][6][7] as well as block-copolymers [8] that would otherwise be difficult to obtain. ADMET polymerizations are step-growth polymerizations that lead to high molecular weight polymers, since high conversions can be obtained in a straightforward fashion if modern metathesis initiators are applied.…”