Mechanisms of electroless metal plating. III. Mixed potential theory and the interdependence of partial reactions

Electroless plating reactions are classified according to four overall reaction schemes in which each partial reaction is either under diffusion control or electrochemical control. The theory of a technique based on the observation of the mixed potential as a function of agitation, concentration of the reducing agent and concentration of metal ions is presented. Using this technique it is shown that in electroless copper plating the copper deposition reaction is diffusion-controlled while the formaldehyde decomposition reaction is activation-controlled. Values of the kinetic and mechanistic parameters for the partial reactions obtained by this method and by other electrochemical methods indicate that the two partial reactions are not independent of each other.Nomenclature a Tafel slope intercept - A electrode area - b _M Tafel slope for cathodic partial reaction - b _R Tafel slope for anodic partial reaction - B _M diffusion parameter for CuEDTA^2– complex - diffusion parameter for dissolved oxygen - B _R diffusion parameter for HCHO - C _M bulk concentration of copper ions - bulk concentration of dissolved oxygen - C _R ^a surface concentration of HCHO - C _R bulk concentration of HCHO - D _R diffusion coefficient of HCHO - E electrode potential - E _M thermodynamic reversible potential for the metal deposition reaction - E _M ⁰ standard electrode potential for copper deposition - E _MP mixed potential - E _R thermodynamic reversible potential for reducing agent reaction - E _R ⁰ standard electrode potential for HCHO - F Faraday constant - i _M current density for metal deposition - i _M total cathodic current density - i _M ^k kinetic controlled current density for metal deposition - i _M ⁰ exchange current density for metal deposition - i _M ^D diffusion-limited current density for metal deposition - i _M ^D diffusion-limited current density for total cathodic reactions - current density for oxygen reduction - i _plat plating current density - i _R current density for HCHO oxidation - i _R ⁰ exchange current density for HCHO oxidation - i _R ^D diffusion-limited current density for HCHO oxidation - n _M number of electrons transferred in metal deposition reaction - n _R number of electrons transferred in the HCHO oxidation reaction - R gas constant - T absolute temperature - stoichiometric number - _M transfer coefficient for metal deposition - _R transfer coefficient for HCHO oxidation - _M symmetry factor - number of steps prior to rate determining step - _M overpotential for metal deposition - _R overpotential for HCHO oxidation - v kinematic viscosity - rotation rate of electrode     

Meaning of molecular weight measurements of gum arabic

Summary The weight-average M_W and number-average M_n molecular weights of gum arabic are identical after a proteolysis treatment with pronase. The value (1.8×10⁵) is closed from M_n early reported in the literature whereas M_W before treatment are dispersed for a large lot of samples up to more 10⁶. This can be interpreted by the wattle blossom model for which some homogeneous chains of molecular weight c.a. 2.10⁵ are still linked to a protein core, the crude gum being a mixture of this complex and free chains.     

Novel initiating system based on AlCl3 etherate for quasiliving cationic polymerization of styrene

Summary Quasiliving cationic polymerization of styrene was obtained in the system 2-phenyl-2-propano-/AlCl₃·OBu₂/Bu₂O in a mixture of 1,2-dichloroethane and n-hexane (55:45 viv) at -15 °C. The molecular weights of the polymers (M_n) increased in direct proportion to the monomer conversion. However, the experimental M_ns are essentially higher than theoretical ones, indicating that slow initiation relative to propagation takes place. The molecular weight distributions were broad (M_w/M_n2.5), probably due to the slow initiation and slow exchange between reversibly terminated and propagating species.     

Living cationic polymerization of vinyl ethers with a functional group

Summary Living polymerizations of 2-vinyloxyethyl methacrylate and 2-vinyloxyethyl cinnamate were successfully performed with a mixture of hydrogen iodide and iodine (HI/I₂) as an initiating system in toluene at –15 to –40 °C, Although the two monomers have an unsaturated ester pendant group, their living polymerizations proceeded exclusively via the vinyloxyl group without undesirable side reactions of the pendant group. The product polymers had a very narrow molecular weight distribution (Mw/Mn 1.1), and {Mn} directly proportional to monomer conversion. For both vinyloxyethyl monomers, the addition of a new feed of monomer to a polymerization mixture led to an increase in polymer molecular weight which was again proportional to the conversion.     

Structure and molecular weight of catenapoly [diphenoxy-λ5-phosphazene-co-bis(sulfophenoxy)-λ5-phosphazene] obtained from catenapoly (diphenoxy-λ5-phosphazene) in very strong acid medium

Acid polymers, –[N=P(OC₆H₅)_2–x (OC₆H₄SO₃H) _x ] _n (II), having an entirely inorganic chain of fifth-group elements, with acid equivalent values between 2.90 and 5.19 mEq/g and molecular weights (M _w) of 10⁵–10⁶ (205n3582), have been obtained from –[N=P(OC₆H₅)₂]– _n (I), 4325n 20,300, in very strong acid medium (SO₃/–P=N –=1.15–3.10 mol/mol). Sulfonation of the pendant substituents occurs first in the meta position and successively at the para carbons, presumably due to reduced conformational mobility as the degree of substitution (x) in II increases.     

[η]-M-relationship for polyacrylamide in aqueous 0.1 M Na2SO4 solution

Summary The intrinsic viscosity [] and the molecular weight M_W of 8 pure, unbranched polyacrylamide (PAAm) samples — prepared in our laboratory — were determined and lead to the following formula [] = 0,0194 · M_W ^0,70(cm³/g) Solvent: aqeous 0.1 M Na₂SO₄ solution; T=298K; M_W/M_n-2,5 . In addition a comparison to the []-M-relationships of PAAm in other solvents is given.     

Novel Neodymium-Based Ternary Catalyst, Nd(Oi-Pr)3/[HNMe2Ph]+[B(C6F5)4]-/i-Bu3Al, for Isoprene Polymerization

Summary Polymerization of isoprene was investigated by using a novel ternary catalyst system composed of neodymium(III) isopropoxide (Nd(OiPr)₃), dimethylphenylammonium tetrakis(pentafluorophenyl)borate ([HNMe₂Ph]⁺[B(C₆F₅)₄]^-; borate), and triisobutylaluminum (i-Bu₃Al). The mole ratios of borate and aluminum compounds to Nd catalyst significantly affected the polymerization behavior. Both yield and cis-1,4 content of polyisoprene decreased in the case of [borate]/[Nd] < 1.0, while at [borate]/[Nd] > 1.0 the formation of multiple active species resulted in the polymer showing bimodal peaks in GPC. When the [Al]/[Nd] ratio was lower than 30, the polymer yield sharply decreased, whereas the cis-1,4 content became relatively low with use of a large excess of Al ([Al]/[Nd] > 50). Thus, the optimal catalyst composition was [Nd]/[borate]/[Al] = 1/1/30, which gave in > 97% yield polyisoprene with high molecular weight (M_n2×10⁵) and relatively narrow molecular weight distribution (M_w/M_n2.0) and mainly cis-1,4 structure (90%).     

The relation between melt flow properties and molecular weight of polyethylene

The non-Newtonian behavior of commercial linear polyethylene samples and their fractions were studied at 190°C. The viscosity η versus shear rate \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} curves of whole polymers could be superimposed onto a single master curve despite the variations of their molecular weights and molecular weight distributions. For fractions, however, the same master curve was inapplicable, and the sensitivity of the viscosity to shear rate was found to be greater than those of the whole polymers. The zero-shear viscosities η₀ of fractions were related to the 3.42 power of the weight-average molecular weight M_u as follows: For whole polymers, the zero-shear viscosities were found to be considerably higher at the same M_w and markedly lower at the same z-average molecular weight M_z than those of the fractions. Thus, it was concluded that η₀ corresponds to an average of molecular weight between M_w and M_z. It was found that the molecular relaxation time τ is proportional to M_z^5.3 for whole polymers and to η₀M_w for fractions. Using these relations it was possible to relate the flow ratio, the ratio of flow rates at two different shear stresses, with the molecular weight distribution.     

Preparation and glass transition temperature of hyperbranched poly[allyl methyl maleate‐co‐N‐propyl maleimide]

The kinetics and molecular weight averages of the hyperbranched polymers formed by the alternating copolymerization of equimolar allyl methyl maleate (AMM) and N‐n‐propyl maleimide (PMI) were investigated. The yields, molecular weight averages, and polydispersity indices as well as the branching degrees of the produced copolymers increased with increasing initiator concentrations and prolonged polymerization time. The trends of the experimental molecular weights as determined by size exclusion chromatography were in good agreement with the theoretical predictions. The molecular weight distribution indices fit the curve given by M_w/M_n = 1/(1‐x_D), and the molecular weights fit the curve given by M_w = 4076/(1‐x_D)², where x_D was the conversion of vinyl groups. DSC studies demonstrated a nonlinear relation of T_g values to the reciprocal of molecular weight (M), and T_g values decreased with the increase of molecular weight. For the T_g values of highly branched polymers in high molecular weight range, a relation of T_g = T + k/M was obtained, where T was obtained by extrapolating to infinite molecular weight and k was a constant. T was 136°C, and k = 2.9 for this work. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1941–1947, 2005     

Multichemical defense of plant bugHotea gambiae (westwood) (Heteroptera: Scutelleridae)

Chemical defense in larvae of the plant bugHotea gambiae has been investigated. Results of analyses (GC, GC-MS) on the secretions from the three dorsally situated larval abdominal defense (scent) glands are reported. The secretion from the first abdominal gland consists of a mixture of C₁₀ and C₁₅ isoprenoids: (C₁₀) -pinene, -pinene, limonene, -phellandrene; (C₁₅) -caryophyllene, caryophyllene oxide, -humulene, and (the major component) humulene epoxide II. The secretions from the second and third abdominal glands are similar mixtures consisting of (E)-2-decenal, (E)-4-oxohex-2-enal, andn-tridecane together with lesser amounts of (E)-2-hexenal,n-dodecane, and other materials. Isoprenoid defense is now known from four species of plant bugs (Heteroptera) associated with Malvaceae.     

The importance of site isolation and phase cooperation in propane ammoxidation on rutile-type vanadia catalysts

Propane ammoxidation to acrylonitrile over rutile-type vanadia catalysts is discussed regarding phase cooperation and site isolation effects. Compared with the pure phases, biphasic catalysts with both SbVO₄and -Sb₂O₄are considerably more selective to the formation of acrylonitrile. It is demonstrated that cooperation between the phases during the calcination of the catalyst and the use in propane ammoxidation results in spreading of antimony species from free antimony oxide to the surface of SbVO₄, forming Sb⁵⁺–V³⁺/V⁴⁺supra-surface sites being involved in the formation of acrylonitrile. Dilution and isolation of the vanadium centers in SbVO₄through the partial replacement with, e.g., Al, Ti and W improves the catalytic properties. Structure–reactivity correlations using data for a nominal Sb_0.9V_0.9-x Ti _x O _y series indicate that the activation of propane occurs on a V³⁺site and the activation of ammonia requires an Sb⁵⁺site.     

New Poly(Methacrylate)s Containing Benzylpiperazine and Methylpiperidine Moieties

The synthess of two new methacrylate esters containing 2-(4-benzyl piperazin-1-yl)-2-oksoethyl and 2-(4-methylpiperidin-1-yl)-2-oksoethyl group are described. The monomers produced from the reaction of corresponding 4-methylpiperidinechloroacetamide and 1-benzylpiperazinechloroacetamide with sodium methacrylate were polymerized in DMSO solution at 65°C using AIBN as an initiator. The monomers and their polymers were characterized by IR, ¹H- and ¹³C-NMR spectroscopy. The glass transition temperature of the polymers were investigated by DSC and the apparent thermal decomposition activation energies (E _d ) were calculated by Ozawa method using the SETARAM Labsys TGA thermobalance. By using gel permeation chromatography, weight average ( ) and number average ( ) molecular weights and polidispersity, indices of the polymers were determined.     

Initial rate of alternating copolymerization of anethole with maleic anhydride in methyl ethyl ketone analysis by a complex model

Summary Dilatometrically determined initial rate of alternating copolymerization of anethole (M₁) and maleic anhydride (M₂) in methyl ethyl ketone (MEK) is reported for the total monomer concentrations of 1M, 2M and 3M polymerized at 50°C with AIBN. The rate is larger than the first order with respect to the monomer concentration. The simplified complex model adopted by Shirota et al is found to be consistent with the data. The equilibrium constant of donor-acceptor complexation (C) of the comonomers is measured to be K=0.057 M^–1 in MEK at 26°C. The ratios of the propagation rate constants are calculated to be k_1c/k₁₂=_D=2 and k_2c/k₂₁=_A=6.     

Electron pair donors in carbocationic polymerization

Preparatory to a detailed presentation of a large body of accumulated information, representative data have been selected to demonstrate that well-defined narrow molecular weight distribution (MWD) (¯M_w/¯M_n = 1.1) polyisobutylene (PIB) can be readily prepared in the M_n = 1000 – 100,000 range in the presence of certain types of electron pair donors (EDs) under a great variety of conditions. Specifically, many initiating systems, such as dicumyl chloride/BCl₃, dicumyl alcohol/BCl₃, 2-chloro-2,4,4-trimethylpentane/TiCl₄, that induce nonliving polymerizations and/or give relatively broad MWD PIBs, in the presence of suitable EDs, e.g., dimethyl sulfoxide (DMSO), dimethyl acetamide (DMA), give rise to living polymerizations and yield narrow MWD products. Evidently, by the use of select EDs various undesirable side reactions, i.e., uncontrolled initiation, chain transfer, irreversible termination, indanyl end-group formation, etc., that plague carbocationic polymerizations and which therefore yield ill-defined relatively broad MWD products, can be eliminated and well-defined narrow MWD products can be obtained. The addition of EDs to otherwise extremely rapid carbocationic polymerizations results in lower controlled rates. All these observations and beneficial effects can be explained by controlled carbocation stabilization by EDs, a subject that will be explored and discussed in detail in this series of publications.Paper XXV in the series living carbocationic polymerization     

Influence of Rare Earth (Ce, Sm, Nd, La, and Pr) on the Hydrogenation Properties of Chloronitrobenzene Over Pt/ZrO2 Catalyst

The effect of rare earths (Sm, Pr, Ce, Nd, and La) on the hydrogenation properties of chloronitrobenzene (CNB) over Pt/ZrO₂ catalyst was studied in ethanol at 303K and normal pressure. The results show that the hydrogenation of CNB can be carried out over Pt/ZrO₂ catalyst. The order of the hydrogenation rates of CNB is p>m>o, and the yield of chloroaniline (CAN) is p>o>m. The specific rate constant turnover frequency (TOF) expressed per surface Pt atom increases when the platinum catalyst is modified by rare earth. The conversion of CNB is >99% and CAN is the main product in the hydrogenation of CNB over PtM/ZrO₂ catalysts. The PtPr/ZrO₂ catalyst shows the best selectivity of CNB to CAN: 89.4mol% for o-CAN, 94.6mol% for m-CAN and 95.1mol% for p-CAN.     

Living carbocationic polymerization

Summary Living carbocationic polymerization (LCPzn) of isobutylene (IB) has been achieved by the 2-chloro-2, 4, 4-trimethylpentate (TMPCl)/TiCl₄ initiating systems in the presence of KCl in conjunction with the 18-crown-6 ether in CH₂Cl₂/hexanes solvent mixture at –80°C. The rate of initiation is relatively slow and the molecular weight distribution (MWD) of the polyisobutylene (PIB) becomes narrower (M_w/M_n decreases from 1.8 to 1.2) in the course of incremental monomer addition (IMA). In the presence of the crown ether, and depending on its concentration, the charges become highly viscous rendering stirring difficult and preventing the synthesis of M_n's in excess of 15, 000 g/mole.     

A Study of Sodium–Copper and Sodium–Nickel Polyphosphate Glasses by Differential Scanning Calorimetry1

Sodium polyphosphate and sodium–copper and sodium–nickel copolyphosphate glasses (with the ratio Na : M = 9 : 1 and 8 : 2, where M is Cu or Ni) are studied. The glass transition (T _g) and melting (T _m) temperatures are determined by differential scanning calorimetry (DSC). It is revealed that the T _gand T _mtemperatures depend on the molecular weight M _t(determined from terminal groups) of polymeric glasses, the Na : M ratio, and the glass synthesis conditions. The activation energies are calculated, and the thermodynamic parameters H, S, and C _pare measured.     

Poly(N-propargylamide)s bearing cholesteryl moieties: Preparation and optical activity

We synthesized a novel chiral cholesteryl-based N-propargylamide (M_ch, HCCCH₂NHCOCH₂CH₂COOch, ch = cholesteryl) from which homopolymers [P(M_ch)] with different molecular weights (number-average molecular weight: 8600, 14100 and 30000) were prepared. The polymers formed helical structures with a preferential helicity. The three polymers increased in both helix content and specific rotation as the molecular weight increased. P(M_ch)-8600 was studied in detail as the model polymer. P(M_ch)-8600 adopted helical conformations in toluene, THF, CHCl₃ and CH₂Cl₂, exhibited thermal stability with a decomposition temperature of 273 °C and formed a lyotropic liquid crystal under the studied conditions. Copolymers of different compositions of M_ch and an achiral monomer (M_et) were prepared. The copolymers formed helices to different degrees depending on the specific composition, indicating an effective approach for controlling the formation of helices in synthetic helical polymers.     

Properties of some polysilane polymers: (n-PrSiMe)n, (i-PrSiMe)n, and (sec-BuSiMe)n

Three polysilane polymers, (n-PrSiMe) _n , (i-PrSiMe) _n , and (sec-BuSiMe) _n , were synthesized and characterized by DSC. UV spectroscopy, wide-angle X-ray diffraction, and optical microscopy, all at variable temperatures. The known thermochromic transition of (n-PrSiMe) _n at 48 C is associated with a change from an orthorhombic to an isotropic phase. (i-PrSiMe) _n was examned as an insoluble and soluble (lowM _w) fraction, both existing mainly in an orthohombic lattice at room temperature. (sec-BuSiMe) _n has a mesophase structure at 25 C, undergoes a weak endothermic transition to a second (nematic) mesophase near 65 C, and becomes isotropic at 160 C.Dedicated to the memory of Professor Zygmunt Lasocki, a fine chemist and a kind and gentle person.     

New main chain nonlinear optical polymers with high glass transition temperatures

Summary Various 4-methoxy-4-carbomethoxy--amino--cyanostilbenes were prepared as mixtures of E and Z isomers, and polymerized via condensation polymerization using dibutyltin diacetate as catalyst. The resulting low molecular weight homopolymers showed higher glass transition temperatures (168–183°C) than previously reported main chain nonlinear optical (NLO) homopolymers. A high molecular weight (M_n30, 200) copolymer possessed an even higher glass transition temperature of 187°C. The hyperpolarizability of the polymers and a model compound were found by EFISH measurements to be in the range of 61 to 79x10^-48 esu.