The morphology of ADMET-synthesized polyethylene with n-butyl branches precisely spaced on every 39th carbon (EH39) was studied in comparison with an ethylene/1-hexene addition copolymer possessing the same branching probability, the goal being to elucidate the effect of the intramolecular sequence length heterogeneity on the lamella crystal thickness and its distribution. EH39 was found to have an orthorhombic crystalline polymorphism, which is normal for commercialized polyethylenes and different from that of the other ADMET polyethylenes with shorter CH 2 spacing (C15, C21). EH39 exhibits a narrow lamella thickness distribution; the average thickness (l c,av. ) corresponds exactly to the space length between two consecutive branches, suggesting the complete exclusion of n-butyl branches from the crystal stem. The average thickness, l c,av. mentioned above is also coincident with that obtained from WAXS and SAXS. On the other hand, the 1-hexene copolymer forms much thicker lamellae and a broader thickness distribution than ADMET polyethylene. Here, the average thickness l c,av. determined by TEM observation of the copolymer is 1.5 times larger than that calculated from the most probable ethylene sequence length obtained from 13 C NMR, or for a theoretical ethylene sequence length distribution, indicating that the lamellae are composed predominantly of the sparsely branched longer ethylene sequences that are statistically included. The intramolecular sequence distribution is considered significant to determine the lamella thickness and thickness distribution for short chain-branched polyethylenes with a narrow intermolecular chemical composition distribution.

Lamella thickness distribution (LTD) plays a critical role in determining the mechanical properties of polyethylene. LTD is predominantly governed by the intermolecular chemical composition distribution, but intrachain heterogeneity also results in a broadened LTD. Polyethylene synthesized by acyclic diene metathesis (ADMET) contains pristine microstructures free from inter and intrachain heterogeneity and therefore represent ideal models to investigate these phenomena. The crystalline structures of ADMET polyethylene with ethyl or n-hexyl branches every 21 st backbone carbon (EB21and EO21, respectively) were characterized by transmission electron microscopy (TEM), small X-ray scattering and wide angle X-ray diffraction (SAXS and WAXD), and differential scanning calorimetry (DSC). The samples were crystallized for various periods at temperatures near the DSC crystallization peak temperatures: 10 8C for EB21 and 0 8C for EO21. TEM observation exhibited that EB21 displays straight lamellar crystals with axialitic organization and an average thickness of about 55 Å. This corresponds to twice the ethylene sequence length between branches, suggesting that one lamellar stem spans three branches and includes one ethyl branch within the lamella. The lamella thickness distribution was very narrow compared with that of the cross-fraction of ethylene/1-butene copolymer prepared via Ziegler-Natta polymerization. Similarly it was found from the same characterization methods that EO21 also displays a narrow lamella thickness distribution albeit with thinner lamellae, averaging 25-26Å thick. Judging from this lamella thickness, EO21 is considered to have a lamella stem composed of a single ethylene sequence between two braches, suggesting that the n-hexyl branch is entirely excluded from a crystalline phase.

We present a method for the synthesis of soluble and processable 3,4-alkylenedioxypyrrole (XDOP)-based conjugated polymers via an iododecarboxylation-deiodination polymerization methodology. Polymerization to the respected PXDOP derivatives of suitably high molecular weight (3.8-14.2 kDa vs polystyrene as measured by GPC) was achieved by either heating the neat monomers for a few hours or allowing them to remain at room temperature for several days. A family of four polymers was synthesized and characterized optically and electrochemically. Polymer solutions were transparent in the visible in their neutral states, red in their partially oxidized states, and grayish-green in their heavily oxidized states. Electrochemical measurements of cast films show that all redox processes occur at low potentials (ca. 0 V vs the Fc/Fc + ), similar to electrodeposited films. Polymers spray-cast as films onto ITO exhibited high band gaps above 3.0 eV along with stable UV and near-IR electrochromism in organic solvents with almost no change in the visible. An amphiphilic polymer functionalized with oligoethoxy substituents exhibited enhanced electrochemistry in aqueous electrolyte and high-contrast electrochromism with respect to the nonpolar functionalized polymers in the visible and near-IR.

A structural investigation of linear ethylene-covinyl amine (EVAm) copolymers having a primary amine branch on every 9th, 15th, 19th, or 21st carbon along the ethylene backbone has been completed using step polymerization chemistry. Acyclic diene metathesis (ADMET) polymerization has been used with symmetrical α,ω dienes containing protected amine groups to afford polymers with exact primary structures and constant methylene run lengths between branches. The effects of subtle structural changes such as the ethylene run lengths between amine branches can be observed and used to correlate structure property relationships. NMR and FT-IR techniques are used to characterize and verify the excellent structural control this synthetic approach provides over traditional chain polymerization techniques. Thermal decomposition of these copolymers is shown to additionally support polymer structure while differential scanning calorimetry demonstrates crystallinity in the polymers with an amine on every 15th and 21st carbon, whereas the polymer with an amine on every ninth carbon is amorphous. Variations of the physical and spectral properties are discussed as a consequence of the amine branch spacing, protection, and saturation of the ethylene backbone.

Polyethylene‐based polymeric prodrugs have been prepared by acyclic diene metathesis (ADMET) polymerization; this condensation type, step growth polymerization, affords controlled polymer architectures via exact methylene run lengths between drug branches. Polyethylene was synthesized with the nonsteroidal anti‐inflammatory drug (NSAID) branches ibuprofen and naproxen attached at every 21st backbone carbon through a hydrolysable ester linkage. These ester linkages can have their reactivity tuned by using a variety of spacers that link the drug to the polymer backbone. Two types of spacers, tetraethylene glycol (TEG, hydrophilic) and decanediol (hydrophobic), were incorporated between the drugs and the polymer backbone to observe the effect of spacer properties on the rate of drug release. The rate of hydrolysis and subsequent release of drug was monitored as a direct effect of the spacer and type of reactive linker. With the primary structure of the polymers perfectly known, making such subtle changes to these structures has a dramatic influence on their physical properties. The polymers discussed herein are characterized with NMR, IR, TGA, and DSC. The rate at which these materials hydrolyze and release their pharmaceutical species via enzymatic or chemical hydrolysis was monitored by UV‐vis. Tailoring the type of spacer and hydrolysable linker to a particular drug offers a new class of polyethylene with controllable features that can be used in the application of a new drug delivery material.magnified image