The polyhomologation of 1-boraadamantane: mapping the migration pathways of a propagating macrotricyclic trialkylborane

Trialkyl and triaryl organoboranes undergo multiple, repetitive homologations upon reaction with dimethylsulfoxonium methylide (1). This multiple homologation reaction, or polyhomologation, produces polymethylene in a living reaction. Applying the polyhomologation reaction to cyclic and polycyclic organoboranes permits the construction of unique oligomeric and polymeric architectures that are not readily accessible by standard olefin polymerization. The polyhomologation of 1-boraadamantane.THF (2) by ylide 1 generates novel macrotricyclic trialkylboranes (3). The oxidation of these macrocyclic organoboranes generates a three-armed star polymethylene polymer (4) incorporating a cis,cis-1,3,5-trisubstituted cyclohexane core. Interestingly, only one-third of the initiators lead to product formation, resulting in an observed degree of polymerization 3 times higher than expected. Close examination of the initial stages of polymerization show that 1-boraadamantane.THF reacts with 1 equiv of 1 to afford a monohomologated product. Subsequent homologations were found to contain branch points leading to isomeric tricyclic products after the third, fourth, and fifth methylene insertions. At these stages of homologation, all of the propagating species result in tricyclic trialkylborane cages with collapsed, inverted pyramidal boron centers that are substantially less reactive toward ylide. Approximately two-thirds of the species discontinue polymerization at these stages. However, one-third of these species continue to propagate and eventually result in the formation of giant macrotricyclic polymers of narrow polydispersity. Molecular modeling and kinetic simulation have aided in the analysis of the probable pathways through which the reaction proceeds.     

1-Boraadamantane blows its top, sometimes. The mono- and polyhomologation of 1-boraadamantane

[reaction: see text] 1-Boraadamantane.THF (3) reacts with 1 equiv of dimethylsulfoxonium methylide (4) to afford a monohomologated product. The polyhomologation of 1-boraadamantane.THF by ylide 4 followed by oxidative cleavage generates star polymethylene polymers incorporating a cyclohexane core. However, only one-third of the initiators lead to product formation, resulting in an observed degree of polymerization three times higher than expected. The polyhomologation of 3 was found to contain branch points after the fourth and fifth methylene insertions. At the branch points, the propagating species either terminate in tricyclic trialkylborane cages with collapsed, pyramidal inverted boron centers that are unreactive toward ylide or they continue in uninterrupted polymerization and eventually result in the formation of giant "tube-like" structures such as 5.     

Comparative study on post‐polymerization modification of C1 poly(benzyl 2‐ylidene‐acetate) and its C2 analog poly(benzyl acrylate)

The present study investigates the challenging approach of post‐polymerization modification on polymers with a sterically demanding reaction center. Therefore, the general possibility to functionalize polymethylene moieties was investigated. Poly(benzyl 2‐ylidene‐acetate) was synthesized by polymerization of benzyl 2‐diazoacetate utilizing [(L‐prolinate)Rh^I(1,5‐dimethyl‐1,5‐cyclooctadiene)] as a catalyst. Subsequently, the modification of C1 polymerized poly(benzyl 2‐ylidene‐acetate) with amines was analyzed and the obtained data set was compared with experimental data derived for the C2 analog poly(benzyl acrylate). This is the first study on post‐polymerization modification utilizing densely functionalized polymethylenes as starting materials. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 686–691     

CHEMOTHERAPEUTIC POLYMERS. THE SYNTHESIS OF POLYMERS CONTAINING 5-FLUOROURACIL IN THE MAIN CHAIN

1,3-Dialkyl-5-fluorouracil compounds and polymers containing 5-fluorouracil in the main chain were synthesized by the reaction of 5-fluorouracil with alkylbromidcs and polymethylene bromides respectively. The structures of the new compounds and polymers were confirmed by IR and NMR spectra as well as elemental analyses.The factors affecting the polycondensation, such as the temperature and time of the reaction were investigated. The anti-tumor activity of some of the 5-fluorouracil containing compounds and polymers were also measured.     

Low-temperature dispersion related to methylene units of a polymer main chain

Polymers containing dynamically isolated polymethylene segments of various lengths were obtained from the reaction of bisphenol-A-diglycidyl ether with α,ω-diamines. On the basis of the mechanical damping data of these polymers, it was established that the shortest polymethylene segment to show the ?125°C. γ dispersion, characteristic of polyethylene, must consist of at least five carbon atoms.     

Polyhomologation: Synthesis of Novel Polymethylene Architectures by a Living Polymerization of Dimethylsulfoxonium Methylide

Not conventional polymerization of ethylene, but rather the title reaction has allowed access to the ω-functionalized tertiary polymethylene alcohols 1 . The ylide CH₂SOMe₂ is the methylene source in this living polymerization, and the chain length can be set by the initial ratio of ylide to organoborane.     

The boron-catalyzed polymerization of dimethylsulfoxonium methylide. A living polymethylene synthesis

Trialkyl and aryl organoboranes catalyze the polymerization of dimethylsulfoxonium methylide (1). The product of the polymerization is a tris-polymethylene organoborane. Oxidation affords linear telechelic alpha-hydroxy polymethylene. The polymer molecular weight was found to be directly proportional to the stoichiometric ratio of ylide/borane, and polydispersities as low as 1.01-1.03 have been realized. Although oligomeric polymethylene has been the most frequent synthetic target of this method, polymeric star organoboranes with molecular weights of 1.5 million have been produced. The average turnover frequency at 120 degrees C in 1,2,4,5-tetrachlorobenzene/toluene is estimated at >6 x 10(6) g of polymethylene (mol boron)(-1) h(-1). The mechanism of the polyhomologation reaction involves initial formation of a zwitterionic organoborane.ylide complex which breaks down in a rate-limiting 1,2-alkyl group migration with concomitant expulsion of a molecule of DMSO. The reaction was found to be first order in the borane catalyst and zero order in ylide. DMSO does not interfere with the reaction. The temperature dependence of the reaction rate yielded the following activation energy parameters (toluene, DeltaH(++) = 23.2 kcal/mol, DeltaS(++) = 12.6 cal deg/mol, DeltaG(++) = 19.5 kcal/mol; THF, DeltaH(++) = 26.5 kcal/mol, DeltaS(++) = 21.5 cal deg/mol, DeltaG(++) = 20.1 kcal/mol).     

Liquid-crystalline polyesters containing alternating alkylene and oxyalkylene spacers

Three new series of thermotropic polyesters were prepared in which the structural units consisted of two p-oxybenzoyl dyads alternately flanked by a polymethylene segment and an oxyethylene oligomer. In each series the length of the oxyethylene residue was fixed (n = 2, 3 or 4) and the length of the alkylene segment was varied (m = 6-10 and 12). Details of the synthesis and characterization of the polymers are reported. The effect of the parity and length of the oxyethylene and polymethylene segments on the incidence of mesophases and on their thermodynamic parameters is stressed. The substitution of methylene groups by oxygen atoms in the polymethylene spacer of a fourth series of polymer analogues completely inhibited the nematogenicity of the polymers incorporating even powerful mesogens such as the p-oxybenzoyl dyads.     

Synthesis and characterization of poly(N-acyl or N-aroyl ethylenimines) containing various pendant functional groups. I. Copolymers with pendant olefin groups

Decenyl (D) and heptyl (H) oxazolines were copolymerized in o-dichlorobenzene solvent using methyl 4-nitrobenzenesulfonate as an initiator. A series of decenyl/heptyl oxazolines random copolymers (or DH copolymers) with a total degree of polymerization of 100 and narrow molecular weight distribution were obtained. These copolymers are considered as the poly(N-acylethylenimine)s with allyl pendant groups randomly attached to the far end of their polymethylene, (SINGLE BOND)(CH₂)₇(SINGLE BOND), side chains. The polymers were characterized by NMR, FT–IR. Both DSC and x-ray diffractometer demonstrated that the polymers are highly crystalline. © 1996 John Wiley & Sons, Inc.     

A polypyrrole/polymethylene pattern on gold using a micro-contact printing technique

A micro-contact printing technique was used to fabricate a polypyrrole/polymethylene pattern on a gold surface. ω-(N-Pyrroyl)undecanethiol (PyC₁₁SH) acts as ink for the generation of a pyrrole-terminal monolayer patterned on gold. This monolayer-patterned surface functions as a resist for the selective growth of polymethylene by catalytic decomposition of diazomethane on the gold surface. It also functions as a monomer for the electrochemical polymerization of pyrrole on the PyC₁₁SH monolayer-patterned surface. The polypyrrole/polymethylene pattern was fabricated by an electrochemical polymerization method. The polypyrrole was grown on the pyrrole-patterned surface by potential scanning between 0.0 and 1.2 V vs. Ag wire. The thickness of the polypyrrole growth increases with the increasing number of cycles. The structural features of the patterned surface can be determined by scanning electron microscopy and atomic force microscopy. Electronic Publication     

Preparation of syndiotactic polystyrene using the doubly bridged dinuclear titanocenes

As a new kind of dinuclear metallocene four DBDM (doubly bridged dinuclear metallocene) that hold two different bridging units linking two metallocenes have been prepared and their polymerization properties have been pursued. The selected bridging ligands for DBDM were polymethylene and dialkoxy terminated derivatives to bond two cyclopentadienyls and two titanium centers, respectively. The syntheses of new dinuclear metallocenes 5-8 were able to be achieved by the reaction between dinuclear half-titanocenes 1 and 2 and ditrimethylsiloxy terminated derivatives 3 and 4 at −78 °C. The EI mass spectra and ¹H and ¹³C NMR spectral data were very informative to identify their formulations as well as structural features. The polymerization of styrene was conducted by using DBDM 5-8. From the polymerization studies it was found that (i) DBDM 7 and 8 holding 2,2-diethyl-1,3-dipropanoxy (DEP) bridge not only show greater activity but also produce higher syndiotactic polystyrene than DBDM 5 and 6 holding 1,1,4,4-tetramethyl-1,4-dibutanoxy (TMB) bridge between two titanium centers, (ii) activities increase with increase in the polymerization temperature, the amount of cocatalyst and monomer concentration, (iii) the most crucial factor to control the stereoregularity of the resulting polystyrene is the styrene concentration in reaction system, (iv) surprisingly the catalyst structure does not have much effect on molecular weight of the obtained polystyrenes. The most significant feature from this study is that the second bridging dialkoxy terminated ligands connecting two titanium centers likely exert more pronounced influence than the polymethylene bridges between two Cp groups on the activity of the catalyst as well as the stereochemistry of the generated polymers.     

Synthesis,Characterization, and Application of Poly[Substituted Methylene]S

Radical polymerization of fumaric acid derivatives, such as dialkyl fumarates, gave polymers consisting of a less-or nonflexible substituted polymethylene structure. The yield and molecular weight of the polymers produced increased as the bulkiness of the ester substituents increased. For example, when di-t-butyl fumarate was polymerized in bulk with azocyclohexanecarbonitrile (20 mmol/L) at 80°C for 6 h, polymer with M _n of more than 100 000 was produced in more than 80% yield. The polymers obtained were colorless powders and did not melt before degradation at ～250°C, but they were soluble in such organic solvents as benzene, carbon tetrachloride, tetrahydrofuran, and dioxane. A transparent brittle film or fiber was obtained from toluene solution. Some properties and possibilities for application of these polymers are described and discussed.     

Single-crystal model for the bulk crystallization kinetics of poly(ethylene oxide) and polystyrene

Approximations in the Avrami treatment of impingement which arise when the growing crystalline bodies are rods or disks are discussed, with particular reference to the single-crystal model. This model, previously fitted to the isolated primary crystallization of polymethylene, is extended to discuss the growth of the composite lamellar structures, axialites, and spherulites, and is here fitted to the crystallization of poly(ethylene oxide) and polystyrene. Both polymers are found to yield anomalous values of the Avrami exponent when analyzed in terms of the conventional Avrami equation. The new analysis reveals similarities in the behavior of all three polymers. The residual deviations remaining after the fit of the model to polymethylene and poly(ethylene oxide) follow the same pattern, and the temperature dependence of the rate constants associated with the model is similar for all three polymers.     

Synthesis of hyperbranched carbohydrate polymers by ring-opening multibranching polymerization of anhydro sugar

The synthesis of novel hyperbranched carbohydrate polymers, prepared by the ring-opening multibranching polymerizations of anhydro and dianhydro sugars, is described. The hyperbranched carbohydrate polymers were formed by the cationic polymerization of 1,6-anhydro-beta-D-hexopyranose, 1,4-anhydrotetritol, 2,3-anhydrotetritol, and 1,2:5,6-dianhydro-D-mannitol. These polymerizations proceeded without gelation to produce water-soluble hyperbranched carbohydrate polymers with controlled molecular weights and narrow polydispersities. The values for the degree of branching of the polymers were in the range of 0.28-0.50. The polymerization method, which proceeds through a ring-opening reaction by a proton-transfer reaction mechanism, is a facile method leading to a spherical carbohydrate polymer with a high degree of branching.     

Crystallization during polymerization of diazomethane. I. The boron trifluoride catalyzed reaction

The polymerization and crystallization of diazomethane was analyzed starting with various monomer and catalyst concentrations by following the monomer concentration and analysis of the solid polymethylene produced. Electron microscopy, thermal analysis, x-ray diffraction, and viscometry and density determinations were used to characterize the crystals as produced and after etching with nitric acid. The crystals have a fibrillar and a lamellar component and show no regular chain folding of the molecules. The overall process follows only very approximately the path expected for an ideal living-polymer system capable of reaction in solution and in the solid state. For more detailed correspondence, it was necessary to assume two reaction paths and two crystallization paths.     

Asymmetric polymerization of methacrylates

The syntheses of optically active polymers having helical conformation from bulky methacrylates are reviewed focusing on selected topics. The monomers include triphenylmethyl methacrylate and its analogues. Asymmetric anionic polymerization of the monomers gives isotactic, optically active polymers having a helical structure with excess helicity. The isotactic content and the extent of helical‐sense excess depend on the monomer structure and the reaction conditions. In the case of methacrylates, completely isotactic and single‐handed helical polymers can be produced by asymmetric anionic polymerization (helix‐sense‐selective polymerization). Asymmetric radical polymerization is also possible for this class of monomer. Some of the helical polymers show chiral recognition ability toward a wide range of racemic compounds. Polymers having main‐chain configurational chirality are also discussed.     

“点击”反应在制备环状聚合物中的应用

环状聚合物具有不同于线性高分子的独特性质,是一类具有应用前景的新型聚合物材料,但复杂的结构导致其合成过程复杂繁琐.＂点击＂化学由于其高效、可靠、高选择性的特点已成为拓扑高分子合成的新方法,活性自由基聚合（ATRP、RAFT和NMP）具有聚合物结构可控等特点,二者联用为环状聚合物的合成拓宽了思路.本文就近几年＂点击＂反应、＂点击＂反应与活性自由基聚合联用以及其他方法联用在环状聚合物中的应用进行综述.＂点击＂反应与这些方法的结合将在功能性环状聚合物的设计与合成中发挥积极的作用.     

A Supramolecular Strategy for the Synthesis of Cyclic Oligomers and Polymers by Ring Expansion

Ring-opening metathesis polymerization (ROMP) of strained macrocycles is a key method to prepare diverse polymers. However, lack of ring strain in most macrocycles is an impediment to polymerization. In this paper, the polymerization/oligomerization of unstrained macrocycles was achieved using a supramolecular approach, leading selectively to cyclic products. Diphenyl thiourea and other guest molecules were used as additives to the ROMP reaction of unstrained macrocycles. An intermediate host-guest complex leads to the stabilization of the open form of the macrocycle after treatment with Grubbs catalysts, thereby favoring polymerization by inhibiting the ring-closing reaction back to the monomer. This proof-of-concept enables ring-expansion polymerization of unstrained macrocycles leading to cyclic polymers with molecular weights up to 6700 Da.     

两亲性树状聚合物*

树状聚合物及其功能化是近年来高分子科学界的研究热点之一。本文综述了不同类型的树状聚合物,分别有聚酯、聚丙三醇、聚乙烯亚胺等超支化聚合物,聚酰胺-胺、聚丙烯亚胺等树枝状聚合物。通过对树状聚合物末端大量官能团的亲水（亲油）改性可以制备两亲性树状聚合物,改性方法主要有酰胺化反应、酯化反应、麦克尔加成反应等。与通过缩聚反应所得到的上述树状聚合物不同,近年来配位聚合领域出现的通过“链行走”机理形成的树状聚乙烯,引起了高度关注,这方面着重介绍了乙烯与极性单体直接共聚合或者采用链行走与原子转移自由基聚合联用制备两亲性树状乙烯聚合物。最后对两亲性树状聚合物领域的发展前景进行了展望。     

Immortal polymerization: The outset,development, and application

The story of the outset of the concept of immortal polymerization is presented. Immortal polymerization is the polymerization that gives polymers with a narrow molecular distribution, even in the presence of a chain transfer reaction, because of its reversibility, which leads to the revival of the polymers once dead, that is, the immortal nature of the polymers. As a result, immortal polymerization can afford polymers with a controlled molecular weight, the number of polymer molecules being more than that of the initiator. The compound that plays a leading role is metalloporphyrin, in which the metal‐axial ligand bond has an unusually high reactivity. Immortal polymerization can be carried out in the ring‐opening polymerizations of epoxides, episulfides, and lactones by the selection of an appropriate metalloporphyrin as the initiator and a protic compound as the chain transfer agent. Immortal polymerization is an effective method for synthesizing end‐functional polymers and oligomers with narrow molecular weight distributions. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2861–2871, 2000