Narrow Composition Distribution Research Articles

Synthesis and Characterization of Maleic Anhydride Grafted Polypropylene with a Well-Defined Molecular Structure

Despite the commercial importance of maleic anhydride grafted polypropylene (PP-g-MAH), it has long been a scientific challenge to prepare this polymer with a well-controlled molecular structure. This paper discusses a new chemical route that can form PP-g-MAH with desirable MAH content, a single MAH incorporated unit, white color, high molecular weight, and narrow molecular weight and composition distributions. The chemistry involves a unique PP-co-p-BT copolymer as the “reactive intermediate” that can be effectively prepared by metallocene-mediated copolymerization of propylene and p-(3-butenyl)toluene (p-BT), with narrow molecular weight and composition distributions, high molecular weight, and a broad range of p-BT contents. The incorporated p-BT comonomer units provide the reactive sites for the subsequent free radical MAH graft reaction under a suspension condition at a low reaction temperature. The resulting PP-g-MAH polymers were carefully examined by a combination of NMR and GPC measurements, which shows almost no change in polymer molecular weight and distribution and a single MAH incorporation (no oligomerization). The incorporated MAH units increase with the increase of initiator concentration, p-BT content, and reaction time. Evidently, the combination of high reactivity of φ-CH3 moiety, a favorable mixing condition between the reactive sites and chemical reagents in the swollen amorphous phases, and low reaction temperature results in MAH grafting reaction selectively taking place at the φ-CH3 moieties without side reactions (i.e., chain degradation and MAH oligomerization). In addition, this suspension reaction process presents an economic method to prepare PP-g-MAH with high polymer content and easy product purification.

Studies on the Microbial Synthesis and Characterization of Polyhydroxyalkanoates Containing 4-Hydroxyvalerate Using γ-Valerolactone

In this study, the ability of Cupriavidus sp. USMAA2-4 to synthesize polyhydroxyalkanoates (PHA) containing 4-hydroxyvalerate monomer (4HV) was studied through one-stage cultivation using γ-valerolactone as the carbon precursor. The presence of 4HV monomer unit in the polymer was detected through gas chromatography analysis, proving the capability of this wild strain bacterium to produce poly(3-hydrxybutyrate-co-3-hydroxyvalerate-co-4-hydroxyvalerate) [P(3HB-co-3HV-co-4HV)] terpolymer. Existence of a 4HV monomer unit in the PHA produced was further confirmed through (13)C and (1)H NMR analysis. P(3HB-co-88 % 3HV-co-1 % 4HV) terpolymer with the highest PHA content of 63 wt% was obtained through combination of 0.14 wt% C of γ-valerolactone with 0.42 wt% C of oleic acid. Various compositions of P(3HB-co-3HV-co-4HV) terpolymer with 3HV and 4HV compositions ranging from 11 to 94 mol% and from 1 to 4 mol%, respectively, were acquired by manipulating γ-valerolactone and oleic acid concentrations. The molecular weight and the thermal and mechanical properties of four different compositions of terpolymers-P(3HB-co-91 % 3HV-co-1 % 4HV), P(3HB-co-55 % 3HV-co-2 % 4HV), P(3HB-co-27 % 3HV-co-2 % 4HV), and P(3HB-co-9 % 3HV-co-1 % 4HV)-were characterized. Among these terpolymers, P(3HB-co-27 % 3HV-co-2 % 4HV) terpolymer with a molecular weight of 5.7 (10(5) Da) exhibited the highest elongation to break (264 %). The monomer unit compositional distributions of these terpolymers were investigated through acetone-water fractionation analysis. The results suggested that these produced terpolymers had broad 3HV compositional distribution and narrow 4HV compositional distribution.

Ethylene/1-olefin copolymerization behaviour of vanadium and titanium complexes bearing salen-type ligand

Ethylene/1-olefin copolymerization using vanadium and titanium complexes bearing tetradentate [O,N,N,O]-type ligand and EtAlCl2 or MAO as a cocatalyst is carried out. In the presence of the vanadium complex activated with EtAlCl2 is observed (a) negative “comonomer effect”, (b) high comonomer incorporation and narrow chemical composition distribution (CCD), (c) unexpected copolymer microstructure, and (d) increased molecular weight of copolymers when compared with the homopolymer. In contrast, titanium catalyst gives copolymers with lower 1-olefin content and broad CCD. Supported complexes show higher activity, lower 1-olefins incorporation and give copolymers with ultra high molecular weights.

ETHYLENE-1-HEXENE COPOLYMERIZATION WITH A 2,6-DIISOPROPYLPHENOL MODIFIED SUPPORTED ZIEGLER-NATTA CATALYST

研究了新型的改性负载型ZieglerNatta催化剂，以期制备出组成分布较窄的乙烯-α-烯烃共聚物.通过2,6-iPr2C6H3-OH与TiCl4/ID/MgCl2型负载型钛催化剂在室温下的反应可将芳氧基接到催化剂表面，制得一种改性的烯烃聚合催化剂M-cat.改性催化剂对乙烯聚合及乙烯-1-己烯共聚反应的催化活性与未改性催化剂相近，但共单体效应较弱.前者共聚物的1-己烯含量低于未改性催化剂的产物，但组成分布较窄，分子量较高，且共聚物的沸腾正庚烷可溶级分的序列分布较接近无规分布.三异丁基铝为助催化剂所得聚合活性高于甲基铝氧烷活化的体系.改性催化体系的活性中心分布与未改性体系相比有明显的差别.

複合高分子の階層的秩序構造―異種分子鎖の結合性に注目して―

This review reports on hierarchical structures formed by complex polymeric materials such as block copolymers and/or polymer blends. The topics and their principal achievements are as follows. The polymer components used are polyiosprene(I), polystyrene(S), poly(2-vinylpyridine)(P) and poly(4-hydroxystyrene)(H), and almost all the polymer samples were prepared by anionic polymerizations and therefore have narrow molecular and composition distribution. 1) Complex structures from multiblock terpolymer: Undecablock terpolymers of the PISISISISIP type and hexablock terpolymers of the PISISI type with both have much different block chain lengths show hierarchical structures with double periodicity. 2) Periodic and aperiodic tiling structures from star-shaped terpolymers: Bulk structures of IXSYPZ star-shaped terpolymers were observed and simply periodic Archimedean tiling structures and quasicrystalline tiling structures with dodecagonal symmetry have been found. 3) New self-assembly manner of block copolymer/homopolymer blend: A polystyrene-b-poly(2-vinylpyridine)(SP) diblock copolymer and H homopolymer can be mixed together to form periodic two-phase structures because of hydrogene bonding interaction between P and H components. 4) Supramacromolecular self-assembly by ionic bonding interaction: Polystyrene with 13 styrene sulfonic acid units on one chain end and polyisoprene with amino group on one chain end tend to form periodic two-phase structures due to acid/base ionic bonding depending on compositions.

Olefin polymerisation catalysts

This chapter investigates methylalumoxane (MAO)-free new olefin polymerization catalyst systems based on FI Catalysts. The chapter investigates MgCl2 as a cocatalyst for the bis(phenoxy-imine) complexes to develop high performance catalysts based on the complexes. Ethylene polymerizations were performed using the resulting mixture of the dealcoholysis product as an activator. The resulting aluminum species of the dealcoholysis product probably work as in situ alkylating reagents for complexes as well as scavengers in a polymerization system. To confirm the chemically homogeneous catalysis of the systems, copolymerization of ethylene with propylene was performed and the comonomer composition distribution of the resulting copolymer was investigated. Gel permeation chromatography–infrared (GPC–IR) analysis revealed that the copolymer possesses narrow propylene composition distribution, showing that the system is single-site catalyst. GPC analyses indicate that the polyethylenes (PEs) formed with catalyst systems possess narrow molecular weight distributions of 2.66 and 2.67, suggesting that the polymers are produced by single active species.

Tailoring nucleation and growth conditions for narrow compositional distributions in colloidal synthesized FePt nanoparticles

To eliminate compositional and size variabilities between individual binary nanoparticles, it is essential to control the mechanistic steps involved in nanoparticle synthesis. A common method for synthesizing FePt nanoparticles involves the simultaneous decomposition and reduction in iron and platinum precursors, respectively. This simultaneous nucleation and growth method yields wide composition and size distributions. This paper describes and experimentally validates a methodology needed to tighten composition and size distributions for this process. By engineering the surfactant chemistry with tertiary phosphines to tightly bind the iron atoms in the iron precursor, uniform platinum rich seeds form during the initial stages of the synthesis. A thermodynamically preferred heterogeneous nucleation of iron atoms into these uniform platinum seeds in the subsequent stages produces a final dispersion with uniform particle-to-particle compositions. The paper addresses the understanding for optimizing the nucleation and growth sequences for compositional control in FePt nanoparticles.

Mechanistic Control of the Nucleation and Growth Conditions for Narrow Composition Distributions in FePt Nanoparticles

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Crystallization and melting of a polyethylene copolymer:In situ observation by atomic force microscopy

The isothermal crystallization and subsequent melting of a narrow composition distribution polyethylene (PE) copolymer (containing a few mole percent of an α-olefin) was observed by hot-stage atomic force microscopy (AFM). The observations revealed that a thicker lamellae population formed first, followed by a thinner population. This indicated that the crystallization process occurred in two sequential steps. Initially, a single population of uniform lamellar thickness appeared rapidly and progressively occupied the surface. These skeletal lamellae typically ranged in thickness from about 10–15 nm. Progressively, upon isothermal storage, a second, bridging population of lamellae filled in between this initial skeletal population. This second population was thinner with thicknesses of about 4–6 nm. Upon heating, the second, thinner, bridging population of lamellae melted first, leaving the initial, skeletal population, which melted at higher temperatures. These results indicate that PE copolymers crystallize in a stepwise fashion; this was envisioned to begin with a first step in which the thickest lamellae crystallize from the folding of the longest ethylene sequences, followed by a second step in which shorter sequences, constrained between thicker lamellae, crystallize into a population of thinner crystals. The melting of this presumed bimodal population of crystal thicknesses would produce a broad and bimodal endotherm; the bimodal melting endotherm was observed by differential scanning calorimetry. Furthermore, the lamellar thickness dimensions measured by AFM were in approximately the same range as those calculated from the melting endotherm by means of Gibbs–Thompson theory. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Comparison of olefin polymerization behavior of sterically crowded tris(pyrazolyl)borate group 4 metal complexes

The ethylene polymerization and ethylene/α-olefin copolymerization behavior of the sterically crowded tris(pyrazolyl)borate group 4 metal complexes Tp Ms*TiCl 3 ( 1, Tp Ms* = HB(3-mesitylpyrazolyl) 2(5-mesitylpyrazolyl) −), {K[Tp Ms*TiCl 3]} 2 ( 2), Tp Ms*TiCl 2(O-2,4,6- tBu 3-Ph) ( 3), Tp Ms*ZrCl 3 ( 4), Tp MsZrCl 3 ( 5, Tp Ms = HB(3-mesitylpyrazolyl) 3 −), and Tp Ms*HfCl 3 ( 6) were studied with dried-MAO activation in toluene solution. These catalysts all produce very high molecular weight ( M v > 10 6) linear polyethylene. Zirconium catalyst 5 excels in productivity in ethylene homopolymerization and ethylene/1-hexene copolymerization, molecular weight, and hexene incorporation ability. Catalyst 5 produces moderately alternating ethylene/1-hexene copolymer (41 mol% hexene) with ultra-high molecular weight ( M w = 1.3 × 10 6), narrow molecular weight distribution ( M w/ M n = 2.2) and narrow composition distribution with high efficiency.

Formation mechanism and composition distribution of FePt nanoparticles

Self-assembled FePt nanoparticle arrays are candidate structures for ultrahigh density magnetic storage media. One of the factors limiting their application to this technology is particle-to-particle compositional variation. This variation will affect the A1 to L10 transformation as well as the magnetic properties of the nanoparticles. In the present study, an analysis is provided for the formation mechanism of these nanoparticles when synthesized by the superhydride reduction method. Additionally, a comparison is provided of the composition distributions of nanoparticles synthesized by the thermal decomposition of Fe(CO)5 and the reduction of FeCl2 by superhydride. The latter process produced a much narrower composition distribution. A thermodynamic analysis of the mechanism is described in terms of free energy perturbation Monte Carlo simulations.

Synthesis of new 1‐decene‐based LLDPE resins and comparison with the corresponding 1‐octene‐ and 1‐hexene‐based LLDPE resins

AbstractThis article extends the composition of linear low‐density polyethylene (LLDPE) resins to that containing 1‐decene comonomer units, and examines the effects of comonomer (type and concentration) to copolymerization and physical properties of LLDPE resins. CGC metallocene technology, under high temperature and high pressure (industrial reaction condition), was used to prepare three types of well‐defined LLDPE copolymers containing 1‐hexene, 1‐octene, and 1‐decene units. They show high molecular weight with narrow molecular weight and composition distributions, comparative catalyst activities, and similar comonomer effects. However, 1‐decene seems to exhibit significantly higher comonomer incorporation than 1‐hexene and 1‐octene, which may be associated with its high boiling point, maintaining liquid phase during the polymerization. The resulting LLDPE copolymers show a clear structure–property relationship. Melting temperature and crystallinity of the copolymer are governed by mole % of comonomer. The increase of branch density linearly decreases the LLDPE melting point and exponential reduction of its crystallinity. On the other hand, the density of the copolymer decreases with the increase of comonomer weight %, which shows a sharp linear relationship in the low comonomer content. The tensile properties of 1‐decene‐based LLDPE are very comparative with those of the commercial LLDPE resins with similar compositions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 639–649, 2007

Anionic Living Polymerization of Macromonomers: Preparation of (A)n-star-(B)1Star Block Copolymers and Some Properties of the Products Obtained

(4-Vinylbenzyl)polystyrene macromonomer (PStM, Mn = 5.45 × 103, Mw/Mn = 1.03) was living-anionically polymerized by sec-BuLi to produce the (PSt)n- star polymer under high vacuum at room temperature. Then, isoprene (Is) was sequentially copolymerized by (PSt)n- to yield the (PSt)6.1-s-(PIs)1 star block copolymer (Mn = 6.39 × 104, Mw/Mn = 1.04) having a narrow PIs composition distribution. Similarly, the (PIs)6.6-s-(PSt)1 star block copolymer (Mn = 10.8 × 104, Mw/Mn = 1.04) was prepared using (4-vinylbenzyl)polyisoprene macromonomer (PIsM, Mn = 5.19 × 103, Mw/Mn = 1.04). The synthetic route by which the PIs- carbanions copolymerize PStM was found to be unsuitable for preparing (PIs)1-star-(PSt)n. The resultant star polymers and star block copolymers were characterized by a special analysis using a gel permeation chromatograph equipped with a low-angle laser light-scattering detector. The living mechanism of the macromonomers polymerization was discussed from the viewpoint of initiation efficiency. The asym...

Characterization of Random Copolymers by Liquid Chromatography under Limiting Conditions of Adsorption

Liquid chromatography under limiting conditions of adsorption (LC LCA) can be considered as a new tool to perform, simultaneously, molar mass and composition determination of statistical copolymers and to separate copolymer blends as a function of copolymer composition or microstructure. The suitability of LC LCA has been demonstrated for two series of statistical copolymers, poly(styrene-co-methyl methacrylate), poly(S/MMA), varying either in molar mass or composition. The binary eluent consisted of a mixture of n-hexane and THF, containing either 26 or 30 vol.% of n-hexane, respectively, for low and high LC LCA. Two parameters, the ratio of peak area over height and the ratio of peak area of chromatograms obtained by LC LCA and size exclusion chromatography (SEC), were employed to evaluate statistical copolymer elution through LC LCA. From the peak analyses, macromolecule recovery was complete over the entire composition and the molar mass ranges. LC LCA and SEC were further compared, and off-line fractionation was subsequently performed using a combination of both methods, with different statistical copolymer solutions having narrow, broad, and bimodal composition distributions.

Amphiphilic gradient poly(styrene- co-acrylic acid) copolymer prepared via nitroxide-mediated solution polymerization. Synthesis, characterization in aqueous solution and evaluation as emulsion polymerization stabilizer

A well-defined, amphiphilic poly(styrene- co-acrylic acid) copolymer was synthesized in a single step by nitroxide-mediated controlled free-radical copolymerization of styrene and acrylic acid, without protection of the acid groups: M n=6500 g mol −1, M w/ M n=1.5 and a composition of F AA=0.70±0.03 in acrylic acid. In addition to the good control over molar mass and molar mass distribution, the copolymer exhibited a narrow composition distribution with a slight gradient. Such copolymer was an efficient stabilizer for the emulsion polymerizations of styrene and of mixtures of methyl methacrylate and n-butyl acrylate, until 45 wt% solids. A low amount (typically 3–4 wt% based on the monomer(s)) was needed for a good stabilization. This is approximately a decade lower than the required amount of random, amphiphilic copolymers prepared via conventional free-radical polymerization. The performances were, however, below those of analogous diblock copolymers, but the great advantage is the very easy synthetic procedure.

Formation Mechanism of FePt Nanoparticles Synthesized via Pyrolysis of Iron(III) Ethoxide and Platinum(II) Acetylacetonate

In this study the mechanism for the formation of FePt nanoparticles (NPs) via the pyrolysis of iron(III) ethoxide [Fe(OEt)3] and platinum(II) acetylacetonate [Pt(acac)2] is investigated. We have recently reported that monodispersed equiatomic FePt NPs with a mean diameter of 4.5 nm and a narrow composition distribution were successfully synthesized by this route. However, control of the mean size and further narrowing of the size distribution have not yet been achieved. In the present study, we systematically examined variability in the particle size Dp, size distribution σ, and atomic composition of the NPs with changing synthetic conditions such as reaction temperature, rate of temperature increase, and total amounts and input molar ratios of precursors and capping agents. As a result, Dp was varied from 1.8 to 6.8 nm, the best size distribution σ achieved was 16%, and the Fe content of the NPs varied from 29 to 51 atomic %. On the basis of the experimental results, we determined the following important...

FePt Nanoparticles with a Narrow Composition Distribution Synthesized via Pyrolysis of Iron(III) Ethoxide and Platinum(II) Acetylacetonate

Equiatomic colloidal FePt nanoparticles (NPs) of 4.5-nm mean diameter were chemically synthesized using iron(III) ethoxide and platinum(II) acetylacetonate as precursors. All of the starting materials used in the synthesis were stable in air and had relatively low toxicity. Reaction proceeded without any reducing agent, providing an easy and robust way of synthesis of FePt NPs. FePt NPs were characterized by X-ray diffractometry (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray fluorescence spectrometry (EDX), and inductively coupled plasma atomic emission spectrometry (ICP-AES). TEM-EDX analysis revealed that FePt NPs contained little oxygen or other impurities. In addition, the atomic composition distribution of each NP was considerably narrow, and seven out of ten NPs contained Fe and Pt atoms necessary to be transformed into the chemically ordered L10 crystalline structure. By annealing at 600 °C for 30 min, as-synthesized fcc FePt NPs were transformed into the L10 phase and showe...

Melting behavior of polyethylene/α‐olefin copolymers: Narrow composition distribution copolymers and fractions from Ziegler–Natta and single‐site catalyst products

AbstractThe melting temperature and heat of fusion were measured for an extensive series of compositionally uniform copolymers of ethylene with butene‐1, hexene‐1, and octene‐1. Fractions and whole polymers that exhibited minimal interchain compositional heterogeneity were from commercial copolymers made with either Ziegler–Natta (ZN) or single‐site metallocene catalysts. The present results do not support recent claims that ZN and corresponding metallocene catalyst copolymers melt at significantly different temperatures, nor the implication that comonomer incorporation is “blocky” in ZN copolymers. In five of the six comonomer/catalyst systems the dependencies of the melting temperature on comonomer type and amount were scarcely distinguishable. This common behavior is the same as that for a model random copolymer, so we conclude that most ethylene/α‐olefin copolymers have random distributions of ethylene sequences. The exception in the present study is a metallocene ethylene/butene‐1 copolymer that melts at lower temperatures and apparently has perceptibly alternating sequence distributions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3416–3427, 2004

Production and Characterization of Poly(3-hydroxybutyric acid-co-3-hydroxyvaleric acid) from l-Valine by Ralstonia eutropha

Abstract The biosynthesis of polyesters from different l-amino acids was investigated by wild-type Ralstonia eutropha (formerly Alcaligenes eutrophus). The accumulation and degradation of the polyesters was found to occur during the cultivation time from 6 h to 48 h, when R. eutropha was cultivated on nitrogen-poor medium containing 1% (w/v) of each l-amino acid as the sole carbon source by two-step batch fermentation. l-Valine was best among different l-amino acids used for the polyester productivity. The polyester content in dried cells produced from l-valine as the sole carbon source was up to 36 wt % during the cultivation time from 24 h to 36 h in a two-step fermentation and up to 27 wt % during 120 h of culture time in a one-step fermentation, respectively. The compositions and molecular weights of the polyesters produced from l-valine were ca. 90 mol% of 3-hydroxybutyric acid (3HB) and ca. 10 mol% of 3-hydroxyvaleric acid (3HV) units and up to 5 × 105–8 × 105 g mol−1, respectively. As-biosynthesized P(3HB-co-ca. 10 mol% 3HV) was shown to have a random sequence distribution of 3HB and 3HV units by analysis of the 13C NMR spectra and have a very narrow comonomer compositional distribution by the fractionation method with chloroform/heptane mixed solvent.

Synthesis of Linear Polyolefin Elastomers Containing Divinylbenzene Units and Applications in Cross-Linking, Functionalization, and Graft Reactions

This paper discusses the synthesis of linear polyolefin elastomers containing divinylbenzene (DVB) units, including poly(ethylene-ter-propylene-ter-divinylbenzene) (EP-DVB) and poly(ethylene-ter-1-octene-ter-divinylbenzene) (EO-VDB). Several metallocene catalysts were evaluated to identify a system that can carry out monoenchainment of DVB and produce terpolymer with uniform molecular structure. Some resulting EP-DVB and EO-DVB terpolymers prepared by a rac-Et(Ind)2ZrCl2/MAO catalyst show good solubility in common organic solvents, controllable DVB content, high molecular weight, and narrow molecular weight and composition distributions. The uniform terpolymer microstructure also exhibits a DSC curve with a sharp glass transition temperature (Tg) that corresponds to its composition. Some EP-DVB and EO-DVB terpolymers with DVB content <2 mol % show low Tg's, below −45 and −55 °C, respectively. In turn, the pendent styrene moieties in the terpolymers are very versatile and engage in facile thermal and UV cr...