One‐step synthesis and ring‐opening polymerization of novel macrocyclic(arylene multisulfide) oligomers

A series of macrocyclic(arylene multisulfide) oligomers were synthesized under high dilution conditions by reacting diphenyl ether/diphenyl/diphenyl disulfide/diphenyl methane with dichloro disulfide in the presence of a trace amount of iron powder by a one‐step reaction. From MALDI‐TOF mass spectra, it was established that the repeating units of the cyclization ranged from two to seven and the unit of macrocyclic(arylene multisulfide) oligomers had one to seven sulfur atoms. The macrocyclic oligomers readily underwent ring‐opening polymerization in the melt, resulting in linear, high molecular weight polymultisulfides. DSC thermograms demonstrated that the four polymultisulfides, derived from the macrocyclic(arylene multisulfide) oligomers, are amorphous in nature. The macrocyclic(arylene multisulfide) oligomers and polymers were analyzed by MALDI‐TOF‐MS, IR, HPLC, NMR, DSC, and TGA methods. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 735–741, 2004     

Novel aromatic macrocyclic oligomers: intermediates for the preparation of high-performance polymers

Recent studies aimed at the development of macrocyclic oligomers as the intermediates for the preparation of high-performance polymers are reviewed. Efficient methods for the preparation of a range of cyclic oligomers, such as aryl ether ketones, aryl ether phthalazines, aryl ether isoquinolines, aryl ether phthalazinones, and arylene sulfides, have been developed. Cyclization was achieved via a nucleophilic aromatic substitution reaction under high-dilution conditions. The cyclic aryl ether oligomers undergo a facile ring-opening polymerization to form high molecular weight polymer. Cyclic oligomers containing an aromatic sulfide linkage also undergo a facile free-radical ring-opening polymerization to form high molecular weight polymers which can be amorphous or crystalline. Due to their low molecular weights, these cyclic oligomers have very low melt viscosities which makes them attractive intermediates for a variety of applications for which the conventionally prepared high molecular weight polymers would not be suitable.     

Synthesis and properties of poly(4,4′-oxybis(benzene)disulfide)/graphite nanocomposites via in situ ring-opening polymerization of macrocyclic oligomers

An effective method for the preparation of poly(4,4′-oxybis(benzene)disulfide)/graphite nanosheet composites via in situ ring-opening polymerization of macrocyclic oligomers were reported. Completely exfoliated graphite nanosheets were prepared under the microwave irradiation followed by sonication in solution. The nanocomposites were fabricated via in situ melt ring-opening polymerization of macrocyclic oligomers in the presence of graphite nanosheets. The graphite nanosheets and resulted poly(arylene disulfide)/graphite nanocomposites were characterized with field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), tensile tester and electrical conductivity measurements. Compared with pure polymer, the electrical conductivity of the poly(arylene disulfide)/graphite nanocomposites were dramatically increased and had a value of about 10⁻³ S/cm for the nanocomposite containing 5 wt% graphite. The nanocomposites exhibit as both high performance polymeric material and electrically conductive material. Therefore, they show potential applications as high temperature conducting materials.     

Ring-opening polymerization of macrocyclic(aromatic disulfide) oligomer derived from 4,4′-oxybis(benzenethiol)

Ring-opening polymerization of macrocyclic(aromatic disulfide) oligomer derived from 4,4′-oxybis(benzenethiol) was studied. Ring-opening reactions were carried out in nitrogen and oxygen atmosphere, respectively. Oxidation reaction and cross-linking reaction took place in oxygen atmosphere. The melt copolymerization between cyclic 1 and elemental sulfur was studied using DSC, and TGA techniques. With increasing the contents of sulfur in the polymer, the T_g values, and 5% weight loss temperatures decreased. When the ratio of sulfur to cyclic reached 5, the polymer appeared as a rubber with a T_g of 23.0 °C and a 5% weight loss temperature of 269.4 °C. A series of poly(thiol aromatic)s were prepared from cyclic 1 and dibromo aromatic compounds in diphenyl ether at 260 °C. The dibromo aromatic compounds can be bis(4-bromophenyl) ether, 4,4′-dibromobiphenyl, and 1,4-dibromobenzene. 4,4′-Dibromobiphenyl gave poly(thiol aromatic) with a T_g of 122.2 °C and a T_m of 221.3 °C by reacting with the cyclic 1.     

Crosslinking of poly(arylene disulfide)s and poly(arylene sulfane)s derived from cyclic(arylene disulfide) oligomers

Cyclic(arylene disulfide) and polycyclic(arylene sulfide) oligomers were synthesized by catalytic oxidation of arylenedithiols or arylenetrithiols with oxygen in the presence of a copper‐amine catalyst. These cyclic(arylene sulfide) oligomers can undergo free radical ring‐opening polymerization at an elevated temperature in the melt or solution. Polycyclic(arylene sulfide) oligomers can be used to crosslink poly(arylene disulfide)s and poly(arylene sulfane)s derived from cyclic(arylene disulfide) oligomers and elemental sulfur. The crosslinking reactions were investigated by differential scanning calorimetry and by solubility of the cured products. The minimum concentrations of polycyclic(arylene sulfide) oligomers for producing a well crosslinked poly(arylene disulfide) and poly(arylene sulfane) are 7 wt % and 10 wt %, respectively. The crosslinking reactions between poly(arylene disulfide)s, poly(arylene sulfane)s, and triallyl‐1,3,5‐triazine‐2,4,6(1H,3H,5H)‐trione (TTT) were also investigated. TTT is more efficient for crosslinking than the synthesized polycyclic(arylene disulfide) oligomers. The crosslinkable poly(arylene disulfide)s and poly(arylene sulfane)s could be potentially used as high temperature coatings, sealants, adhesives, and as matrices for high performance thermoset composites. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3069–3077, 1999     

Synthesis and ring‐opening polymerization of macrocyclic aromatic sulfide oligomers

A series of macrocyclic(arylene sulfide) oligomers were synthesized by reaction of 4,4′‐oxybis(benzenethiol) with a number of difluoro compounds in dimethylformamide (DMF) in the presence of anhydrous K₂CO₃ under high dilution conditions. The difluoro compound can be 4,4′‐difluorobenzophenone, bis(4‐fluorophenyl)sulfone or 1,3‐bis(4‐fluorobenzoyl)benzene. Detailed structural characterization of these oligomers by matrix‐assisted laser desorption and ionization‐time of flight‐mass spectroscopy (MALDI‐TOF‐MS) demonstrated their cyclic nature. The MALDI‐TOF‐MS technique has proved to be a powerful tool to analyze these cyclics. These cyclic oligomers are amorphous and highly soluble in DMF and N,N′‐dimethyl acetamide. Moreover, these cyclic(arylene sulfide) oligomers readily underwent ring‐opening polymerization in the melt at 285 °C in the presence of 2,2′‐dibenzothiazole disulfide, affording linear, high molecular weigh poly(aromatic sulfide)s. These polymers are insoluble in most common solvents. Copyright © 2004 Society of Chemical Industry     

Fractionation of partially stereoregular poly(propylene oxide)

Partially stereoregular poly(propylene oxide) samples were synthesized via reactions catalysed by a preformed analytically defined trimethylaluminium hydrolysate. These samples were fractionated into two contrastingly different fractions.

1. (i) D-polymers: This fraction constituted the major part (up to 90%). It mainly contained cyclic low molecular weight oligomers (MW < 1000). The linear chains found in D-polymers had hydroxyl end groups. No double bonds could be detected spectroscopically.

2. (ii) K-polymers: This fraction was high molecular weight stereoregular polymer. Stepwise thermal precipitation from dilute isooctane solution of K-polymers yielded a succession of fractions which differed in melting point. It appears that the phase equilibria during the thermal precipitations were not controlled by the molecular weights of species.

Chemical Recycling of Polystyrene by Pyrolysis: Potential Use of the Liquid Product for the Reproduction of Polymer

The potential use of the liquid product obtained from the pyrolysis of polystyrene as a raw material for the reproduction of the polymer was investigated in this study. Catalytic and non‐catalytic pyrolysis experiments were carried out in a fixed bed reactor using either model polymer or commercial waste products as the feedstock. The liquid fraction produced from all the pyrolysis experiments consisted mainly of the styrene monomer and this was subjected to re‐polymerization without any further purification, in a DSC with AIBN initiator. It was found that the pyrolysis oil fraction could be re‐polymerized to again produce polymer. However, aromatic compounds included in this fraction may act as chain transfer agents, resulting in alterations in the shape of the reaction rate curve and lowering significantly the average molecular weight and the T_g of the polymer produced.

     

Molecular weight distribution in disulfide polymers

The published data on molecular weight distribution in polysulfide are rather contradictory and cannot be correlated with the concept of the existence of thiol–disulfide interchange in these polymers. In the present work the viscosity and molecular weights of liquid thiokols have been investigated (the number-average molecular weight by iodometric titration and by ebulliometry and the weight-average molecular weight by the light-scattering method). When measuring the light scattering in Thiokol Solutions a considerable depolarization of the scattered light was observed. This fact must be taken into account in the molecular weight determination. It has been established that in polydisulfides with thiol endgroups thiol–disulfide interchange reactions take place not only during the synthesis, but also in the polymer itself (in bulk). These reactions lead to the formation of polymers with an equilibrium molecular weight distribution. A relation of log η = f(M _w)^½ has been found that can be used in determining the weight-average molecular weight of liquid Thiokols.     

Synthesis of poly(arylene disulfide)–vermiculite nanocomposites via in situ ring‐opening polymerization of macrocyclic oligomers

Exfoliated poly(4, 4′‐oxybis(benzene)disulfide)/vermiculite (POBDS/VMT) nanocomposites were successfully synthesized via in situ melt intercalation of cyclo(4, 4′‐oxybis(benzene)disulfide) oligomers (COBDS) into octadecylammonium‐exchanged VMT (organo‐VMT). The POBDS/VMT nanocomposites were melt fabricated in a two‐step process. First, the COBDS/VMT nanocomposite precursor was fabricated by melt delaminating organo‐VMT with COBDS at a temperature slightly higher than its melting point. Subsequently, exfoliated POBDS‐VMT nanocomposites can be prepared in situ via instant melt ring‐opening polymerization of the COBDS‐VMT nanocomposite precursor. The nanoscale dispersion of VMT layers within POBDS polymer was confirmed by X‐ray diffraction, scanning electron microscopy and transmission electron microscopy. High molecular weight POBDS polymer was formed in a few minutes at the same time as the nanocomposite formation. The results of dynamic mechanical analysis showed that the storage modulus and glass transition temperature of the nanocomposites are much higher than those of the POBDS matrix, even with a very small amount of VMT addition. This methodology provides a potential approach to synthesize high‐performance polymer/clay nanocomposites. Copyright © 2004 Society of Chemical Industry     

Star oligomers for low VOC polyurethane coatings

Conclusion  Hydroxyl functional star oligomers prepared by ring-opening polycondensation have a narrow molecular weight and composition distribution. Such oligomers give a solids/viscosity advantage over linear structures at the same molecular weight and can be used in low VOC two component polyurethane coatings. The solids/viscosity advantage is a combination of the highly branched structure and the narrow molecular weight distribution. Acrylic polyols formulated at the same molecular weight/polarity/average functionality and hydroxyl value give poorer drying properties. This difference can be explained by the fact that the free radical polymerisation technique leads to polymer compositions having a broad molecular weight and functionality distribution and high fractions of polymer with a low functionality. The potlife of acrylic polyols based formulations is adversely affected by the higher fractions of high molecular weight material and with a high average functionality. In low VOC polyurethane formulations star oligomers need to be formulated within a narrow range of compositions (TG, polarity), functionality and molecular weight to get an optimum balance of drying properties and potlife.     

Wholly aromatic polyamide-hydrazides I. A viscometrical method for monitoring of condensation polymerization reactions

A simple and practical viscometrical method for monitoring the progress of condensation polymerization reactions was investigated. It consisted of following the reaction mixture capillary flow time as a function of molar ratio of the reacting monomers in a polymerization reaction performed by gradual addition of terephthaloyl chloride (TCI) into solution of p-aminobenzhydrazide (ABH) in N,N-dimethylacetamide (DMA) solvent. The results obtained were compared to those from dilute solution viscometry and light scattering studies. This indicated that the observed increase in the reaction mixture capillary flow time accurately enough reflected the buildup of the molecular weight of growing polymer product during the course of this course of this condensation polymerization reaction and that this viscometrical monitoring method provided an extremely practical tool for controlled preparation of the polymers of high and/or predetermined molecular weights by this synthetic route. A series of para-oriented, wholly aromatic amide–hydrazide polymers from ABH and TCl, was also characterized by viscometry and light scattering in DMA at 20°C, and the following viscosity–molecular weight relationship was determined: [η] = 5.16 × 10^?4M?.     

Synthesis of polycarbonate containing in-chain 4-N,N-dimethylamino-4′-nitrostilbene via ring-opening polymerization

Summary We have successfully synthesized a new NLO chromophore based on 4-N,N-dimethylamino-4-nitrostilbene which contains bisphenol functionality for polycarbonate preparation. Chromophore-4 was used to make macrocyclic carbonate oligomers and the oligomers were converted to polycarbonate via ring-opening polymerization in solution.     

Novel initiators for the synthesis of propylene oxide oligomers by anionic ring opening polymerization

A series of potassium alcoholates was obtained from the reaction between KOH and ethylene glycol, resorcinol, 4,4′-bisphenol A, 4,4′-(1,3 phenylenediisopropylidene)-bisphenol, 4,4′-sulfonyldiphenol. These salts were employed to initiate the anionic ring opening polymerization of propylene oxide (PO). The molecular weight distribution of the propylene oxide oligomers prepared by this method and the initiator structure were correlated. These oligomers were characterized through Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR) spectroscopies and size exclusion chromatography (SEC). It was found that the molecular weight and polydispersity of the synthesized poly(propylene oxide) (PPO) is highly dependant on the initiator structure and solubility in the reactive medium. The oligomers obtained using di-potassium resorcinolate exhibited a molecular weight distribution more polydisperse than that of PO oligomers synthesized by means of di-potassium ethylene glycolate. In the case of the PO polymerizations started by the potassium salts of 4,4′-bisphenol A, 4,4′-(1,3 phenylenediisopropylidene)-bisphenol and 4,4′-sulfonyldiphenol, the oligomer chains showed very broad molecular weight distributions. In general, lower solubility and augmentation of the polymer polydispersity were observed when the number of aromatic rings in the initiator structure increased. The experimental results were contrasted with those obtained from quantum chemical semiempirical calculations at AM1 level. The peculiar behavior exhibited by the initiators with an aromatic structure could be explained in terms of different reactivities of the initiation sites. The theoretical studies revealed that the ring in the aromatic initiators promotes an unsymmetrical growing when the PPO chains are formed. In contrast, the identical reactivity of both initiation sites in the ethylene glycolate produces a symmetrical growing during the PO polymerization.     

Correction of the number average molecular weight of hydroxylated liquid polybutadiene as determined by vapor pressure osmometry

Summary Number average molecular weight ( ) determinations of oligomers by vapor pressure osmometry (VPO) requires highly purified samples. As ultraviolet spectroscopy is a convenient technique for accurate evaluation of small concentrations, it was used to determine the concentration of 2,6-di-t-butyl-4-methylphenol antioxidant in commercial hydroxylated liquid polybutadiene in the = 28000–3000 range. The data were used to correct values measured by VPO, allowing the determination of correct molecular weights without previous polymer purification.     

Retraction of the claim of ring expansion polymerization of isobutylene

Some three years ago in a preliminary report from this laboratory we have proposed that the polymerization of isobutylene (IB) by the -tolyl--valerolactone/BCl₃ initiating system in CH₃Cl or CH₂Cl₂ diluents at-30°C proceeds in a living manner by an unusual ring expansion mechanism and produces macrocyclic polyisobutylenes (PIBs) [1]. Extensive follow-up research confirmed the living nature of the polymerization, however, has failed to confirm the results of a key preliminary experiment upon which the proposition of macrocyclic polymer structure was based. Thus the results of a comparative hydrolysis/GPC experiment carried out with a relatively low molecular weight (Mn=5,400) PIB at -30°C under a blanket of N₂ which gave a lower apparent molecular weight after hydrolysis than the original sample before hhydrolysis, could not be confirmed with higher molecular weight samples, i.e., with Mn=12,000, 17,000 and 30,000. As a consequence we wish to retract our earlier claim in regard to the synthesis of macrocyclic PIBs by certain lactone/BCl₃ initiating systems but maintain that these polymerizations proceed in a living manner and yield asymmetric telechelic PIBs, e.g.,-chloro--carboxyl-PIBs [2].     

Influence of solvent and molecular weight on thickness and surface topography of spin-coated polymer films

The influence of polymer molecular weight, molecular weight distribution, and polymer-solvent interactions on the thickness and topography of spin-coated polymer films was examined. For films prepared from dilute solutions, highly volatile solvents or fair or “poor” solvents for the polymer adversely affect film surfaces causing nonuniformities (waves) to appear. However, if the concentration of these solutions is increased to approximately the concentration at which entanglements are formed, nearly uniform films are produced even if the solvent employed is highly volatile, such as dichloromethane. When toluene is employed as the solvent, which has a relatively low volatility and therefore forms nearly flat film surfaces, films prepared from dilute solution were found to have thicknesses, h, proportional to η Ω^?0.49 for polystyrene and η Ω^?0.49 for poly(methylmethacrylate) where η_o is the zero-shear rate solution viscosity and Ω is the rotational speed at which the films were prepared. These results suggest that the exponents associated with η_o and Ω may be nearly independent of the type of polymer used as long as flat films are produced. Finally, the molecular weight parameter most important in controlling final film thickness for films made from dilute solutions is M_v, the viscosity-average molecular weight.     

Poly(ester amide)s based on l-lactic acid oligomers and glycine: the role of the central unit of the l-lactic acid oligomers and their molecular weight in the poly(ester amide)s properties

Novel biodegradable poly(ester amide)s (PEAs) based on l-lactic acid (l-LA) oligomers and glycine were successfully synthesized, through an easy and fast procedure, making use of inexpensive starting materials. The l-LA oligomers were prepared with different central units and different molecular weights in order to access the influence of such parameters in the final properties of the PEAs’. Both the central unit of the l-LA oligomer and its molecular weight have important influence in the PEAs’ final properties. The thermal stability is lower for the PEAs containing the l-LA with the shortest central unit and for the PEAs based on the l-LA oligomers of high molecular weight. The PEAs exhibit a semi-crystalline nature, except those derived from the l-LA oligomers with high molecular weight, which have an amorphous character. Both hydrolytic and enzymatic degradation are more pronounced in PEAs synthesized from the l-LA oligomers with low molecular weight. Different mechanisms of degradation were found for the PEAs: bulk erosion and surface erosion, for hydrolytic degradation and enzymatic degradation tests, respectively.     

One step synthesis and rapid ring‐opening polymerization of macrocyclic (arylene thioether ketone) oligomers

Well‐crystal macrocyclic (arylene thioether ketone) oligomers were synthesized under high dilution condition by the reaction of Na₂S with bis(4‐fluoro‐phenyl)‐methanone in 1‐methyl‐pyrrolidone (NMP). The oligomers were fully characterized by Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectra (MALDI‐TOF‐MS), high‐pressure liquid chromatography (HPLC), gel permeation chromatography (GPC), ¹H NMR, ¹³C‐NMR, and differential scanning calorimetry (DSC). According to DSC studies, uncatalyzed and rapid ring‐opening polymerization (ROP) of the oligomers took place instantly when they were heated to melting point. Extracted by dichloro‐methane, the obtained polymer neither loses any weight nor dissolves in boiling 1‐chloro‐ naphthalene. These facts indicated that there are no residual oligomers within the resultant polymer. The as‐prepared oligomers could be potentially used as high‐temperature hot‐melt adhesive at a high temperature > 350°C, and matrices for high‐performance composites and nanocomposites. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 161–166, 2006     

The effect of shear rate on the molecular weight determination of acrylamide polymers from intrinsic viscosity measurements

The rheological response of dilute solutions of high molecular weight polyacrylamides at low shear rates has been measured using a capillary viscometer that provided for a fivefold variation in shear rate at each concentration. The non-Newtonian effects were found to be significant for polyacrylamides with number-average molecular weights exceeding 10⁶. The molecular weight average–intrinsic viscosity relationship most widely used in the literature, [η] = 6.80 × 10^?4M , was found to be valid when [η] was measured at high shear rates where the polymer solutions approached Newtonian behavior. A new relationship was developed relating M _n to the intrinsic viscosity extrapolated to zero shear rate.