Narrow Composition Distribution Research Articles

Synthesis and characterisation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) multi-block copolymers comprising blocks of differing 3-hydroxyvalerate contents

Polyhydroxyalkanoates (PHAs) are attractive alternatives to commodity petroleum derived plastics, being bacterially derived, thermoprocessible and truly biodegradable under ambient conditions. However, the common short chain length PHAs - poly(3-hydroxybutyrate) (P3HB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) - are relatively stiff and brittle, and P3HB in particular has a narrow processing window. Block copolymer synthesis offers an opportunity to produce novel PHA materials comprised of different PHA phases, delivering a potential step-change improvement in PHA properties due to microphase separation. Therefore, this work demonstrates the synthesis and characterisation of novel high molecular weight PHBV-b-PHBV-b-PHBV block copolymers using isocyanate chemistry. High molecular weight, narrow compositional distribution, hydroxy-functionalised PHBV blocks of low (1 mol%) 3HV and high (67 mol%) 3HV contents were used as building blocks. The resulting block copolymers showed a very significant increase in elongation at break (to 76.0 %), as well as improved tensile toughness (to 15.0 MJ/m3) and tensile strength (to 18.5 MPa) compared to the starting materials or comparable blends. Based on the similarity in properties between the 1 mol% 3HV block copolymer products and their counterpart random copolymers, it is also shown that the introduction of urethane linkages had minimal effect on polymer properties. The morphologies of these novel PHBV materials were investigated, supporting the concept that the microphase separation of the different PHBV phases delivered these improved mechanical properties. This approach to PHA-b-PHA block copolymer synthesis offers an attractive generic platform for the production of novel biodegradable PHA materials for film and other applications.

1,3-Pentadiene-Assistant Living Anionic Terpolymerization: Composition Impact on Kinetics and Microstructure Sequence Primary Analysis.

The combination of a living anionic technology and a unique alternating strategy provided an exciting opportunity to prepare novel and well-defined poly(1,3-pentadiene-co-syrene-co-1,1-diphenylethylene) resins consisting of three alternating sequences of modules (A/B/C zwitterions). "A" being Styrene (St)/1,3-pentadiene (PD), "B" being diphenylethylene (DPE)/PD, "A" being DPE/St, respectively, A wide composition range of new polyolefin resins, i.e., poly (A-co-B), poly (A-co-C), and poly (B-co-C), with controlled molecular weight and very narrow molecular weight and composition distributions have been prepared by a one-pot living characteristic method. In the section of kinetic analysis, the terpolymer yields and kinetic parameters were strongly dependent on the feed/comonomer ratio as well as the content of the alternating structure. The competition copolymerization behaviors of A/B, B/C, and A/C were studied in detail in this work. By contrast, the microstructure and the thermal property of the resulting terpolymer were investigated via Nuclear magnetic resonance (NMR) and Differential scanning calorimetry (DSC) analysis. The results of 1H NMR tracking the change of [Aromatic ring]/[C=C] value indicated the distinctive copolymer-ization behavior of the selective "alternating-modules". The glass transition temperature (Tg) was very sensitive to the terpolymer composition. By contrast to poly(A-ran-B) with only one obvious Tg, there were two Tgs in the A/C and B/C copolymerization cases. Moreover, the desirable high Tg ~ 140 °C resin was limited to the terpolymers with up to 50 mol % DPE. Finally, the "ABC-X" mechanism was proposed to interpret the unique terpolymerization behavior, which belongs to the classical "bond-forming initiation" theory.

Characterisation of end groups of hydroxy-functionalised scl-PHAs prepared by transesterification using ethylene glycol

Polyhydroxyalkanoates (PHAs) are a family of biodegradable polyesters with good potential in applications ranging from packaging to implants. The synthesis of block copolymers based on PHAs is one approach to tailoring these physical properties. This work considers the transesterification and end-group characterisation of hydroxy‑terminated PHAs for the chemical synthesis of PHA-based block copolymers. There is currently incomplete knowledge of the relative amounts of the different end-groups in the as-produced materials. Further, the reported hydroxy‑terminated PHAs have relatively low molecular weights (Mn < 4 kDa); hydroxy‑terminated PHAs of intermediate molecular weights (Mn > 20 kDa) - which are more favourable as building blocks for industrially relevant high molecular weight PHA - have not yet been fully characterised for use in such applications, to our knowledge. Here, a more comprehensive strategy for the preparation and characterisation of hydroxy‑terminated PHAs of intermediate molecular weights was applied. Hydroxy-functionalised PHAs were produced via transesterification of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) of differing 3HV contents and with narrow compositional distribution, followed by purification through solvent processing. The functionalised PHAs and reaction by-products were then characterised using FT-IR, 1H-NMR, 13C-NMR, 31P-NMR, GPC and DSC analyses, allowing the determination of the nature and distribution of the end groups. It was found that transesterification does indeed generate both primary and secondary hydroxyl end-groups, while original PHBV materials (PHBpre-sol) had only secondary hydroxyl end groups present. 41% of hydroxy‑functionalised PHBV (PHBtr-sol-D) were likely terminated with either crotonic groups or carboxylic acids. Further, the analysis showed that a proportion of commercial and laboratory derived PHBVs (PHBpre-sol and PHBVpre-sol) was likely dicarboxylic acid-terminated.

2,2‐Bistrifluoromethyl‐4,5‐difluoro‐1,3‐dioxole‐co‐tetrafluoroethylene copolymers with different compositions: Synthesis, chain and condensed matter structures and optical properties

AbstractSynthesis of 2,2‐bistrifluoromethyl‐4,5‐difluoro‐1,3‐dioxole‐co‐tetrafluoroethylene (PDD‐TFE) copolymers with precise chemical structures and understanding effects of the structures on properties are essential for their application. Herein, PDD‐TFE copolymers with different average compositions and narrow composition distributions (NCDs) were synthesized and applied to study the influences of chemical structures on condensed matter structures and optical properties of copolymers. The average length of (PTFE)n sequences were decreased from 7.62 to 1.63, and percentage of TFE in long (PTFE)n sequences (n &gt; 5) decreased from approximately 50% to less than 1%, as PDD molar fraction in the copolymer (FPDD) increased from 13.24% to 52.22%. Consequently, the copolymer with FPDD = 13.24% was semi‐crystalline with a crystallinity degree of 11.57% (determined by WAXD), while the copolymer with FPDD = 52.22% was completely amorphous. The steric energies, glass transition temperatures and transparency of PDD‐TFE copolymers were increased as more cyclic and non‐coplanar structure PDD monomer was incorporated into the copolymers. Refractive indexes of PDD‐TFE copolymers were low and linearly decreased with the increase of FPDD. PDD‐TFE copolymers with high transparencies, low refractive indexes and other excellent properties can be successfully used in the optical fibers and semiconductor fields.

Thermal properties of poly(3-hydroxy-2-methylbutyrate-co-3-hydroxybutyrate) copolymers with narrow comonomer-unit compositional distributions

Thermal properties of poly(3-hydroxy-2-methylbutyrate-co-3-hydroxybutyrate) copolymers with narrow comonomer-unit compositional distributions

Probing Active Sites in CuxPdy Cluster Catalysts by Machine-Learning-Assisted X-ray Absorption Spectroscopy

Size-selected clusters are important model catalysts because of their narrow size and compositional distributions, as well as enhanced activity and selectivity in many reactions. Still, their structure-activity relationships are, in general, elusive. The main reason is the difficulty in identifying and quantitatively characterizing the catalytic active site in the clusters when it is confined within subnanometric dimensions and under the continuous structural changes the clusters can undergo in reaction conditions. Using machine learning approaches for analysis of the operando X-ray absorption near-edge structure spectra, we obtained accurate speciation of the CuxPdy cluster types during the propane oxidation reaction and the structural information about each type. As a result, we elucidated the information about active species and relative roles of Cu and Pd in the clusters.

Ethylene homo- and copolymerization catalyzed by vanadium, zirconium, and titanium complexes having potentially tridentate Schiff base ligands

New potentially tridentate Schiff base ligands, 2-[({4-[(3-N,N-dimethylamino)propyl] phenyl}imino)methyl]-4,6-di-tert-butylphenol (L1H) and 2-[{2-(N-phenyl-N-methylaminomethyl)-phenylimino}-methyl]-4,6-di-tert-butylophenol (L2H) were prepared and after deprotonation they were reacted with VOCl3 or MCl4 (where M = Zr or Ti) to produce corresponding complexes (L1-V, L2-V, L1-Zr, L2-Ti) with good yields. All new compounds were characterized by the 1H and 13C NMR as well as FTIR spectroscopic methods. Upon activation with Et2AlCl or EtAlCl2, both the vanadium complexes exhibited exceptionally high catalytic activities in the ethylene polymerization (up to 69,000 kg/(molV⋅h) for L1-V and 101,500 kg/(molV⋅h) for L2-V) and remarkable thermal stability, and they produced UHMWPE. The complexes of group 4 metals were tested in the ethylene polymerization in conjunction with MMAO and Al(iBu)3/Ph3CB(C6F5)4, and L1-Zr was highly active (11,300 kg/(molZr⋅h)) and L2-Ti was moderately active (750 kg/(molTi⋅h)) when activated with MMAO. Furthermore, L1-2-V/EtAlCl2 systems were found to be very efficient in 1-octene incorporation and they produced copolymers with narrow chemical composition distributions and very narrow molecular weight distributions (Mw/Mn ≈ 2). In contrast to them, the catalysts based on titanium and zirconium complexes in conjunction with Al(iBu)3/Ph3CB(C6F5)4 gave copolymers with very broad comonomer and molecular weight distributions as well as with high molecular weights (Mw = 440,000–690,000 g/mol). It was also found that the chain transfer mechanism involved in the copolymerization process in the presence of vanadium and group 4 metal complexes was different.

The solution copolymerization of styrene and maleic anhydride in a continuous stirred tank reactor and its theoretical modelling

The synthesis of copolymers with a narrow chemical composition distribution (CCD) often requires a technological solution to overcome composition drift. Among the possible solutions, polymerization in a continuous stirred tank reactor (CSTR) is one of the most elegant. During steady state operation, the CCD is only determined by the statistical nature of the copolymerization without any broadening as typically observed in batch reactions. In this contribution, the mathematical description of the copolymerization of styrene and maleic anhydride in a CSTR is provided and experimental data are used to estimate reactivity ratios as well as to describe the copolymer composition as a function of steady state conversion.

The morphology of crystallisation of PHBV/PHBV copolymer blends

The crystallisation of a range of as-produced poly(3-hydroxybutyrate-co-3-hydroxyvalerate) copolymer blends from a mixed culture polyhydroxyalkanoate production process, with low (15%), high (82%) and intermediate (62% and 50%) average 3-hydroxyvalerate (3HV) contents, was studied at different temperatures using polarised optical microscopy, differential scanning calorimetry and X-ray crystallography. The low-3HV content material had narrow compositional distribution and crystallised in the typical highly regular banded spherulite morphology, while the other materials displayed varying degrees of interpenetrating crystallisation of separate crystal phases comprising either the 3HV or 3-hydroxybutyrate (3HB) crystal lattice structure. Because of the differing and competing crystallisation kinetics of these phases coupled with diffusion effects, there was a very strong influence of crystallisation temperature on the resulting morphology. Thus manipulation of the final material properties of such copolymeric materials is dependent on understanding these effects and controlling their processing and crystallisation temperatures and conditions.

Polymer reaction engineering tools to design multifunctional polymer flocculants

A series of multifunctional terpolymers, poly(N-isopropyl acrylamide/2-(methacryloyloxy) ethyl trimethyl ammonium chloride/N-tert-butylacrylamide) [P(NIPAM-MATMAC-BAAM)], were designed to flocculate and dewater oil sands mature fine tailings (MFT). The hydrophobic BAAM comonomer helped in expelling water from the sediments, while the cationic MATMAC comonomer promoted the charge neutralization of negatively charged particles suspended in MFT. The chemical composition distributions of these terpolymers were designed based on the knowledge of the reactivity ratios of all comonomers, instead of by trial and error, as usually done for most polymer flocculants. The binary reactivity ratios of the comonomers were estimated by synthesizing the binary copolymers with various mole fractions of each comonomer in the feed and experimentally measuring the corresponding fraction of comonomer in the copolymers. Polymer reaction engineering tools were used to minimize compositional drift and guarantee the synthesis of terpolymers with narrow chemical composition distributions suitable for MFT dewatering. Focused beam reflectance measurement (FBRM) experiments showed that terpolymers promoted the formation of large MFT flocs (120 μm). The initial settling rate decreased with the increase in flocculant hydrophobicity, likely because the hydrophobic terpolymer segments did not take part in the bridging of the MFT particles. In contrast, the sediment dewaterability increased with the increase in terpolymer hydrophobicity. This study provides guidelines to design a polymer flocculant from first principles and demonstrates the potential of using hydrophobically modified cationic polymers to flocculate MFT effectively.

Dichlorovanadium(IV) diamine-bis(phenolate) complexes for ethylene (co)polymerization and 1-olefin isospecific polymerization

Two vanadium complexes bearing amine-bis(phenolate) ligands with the amino side-arm donor, [V{Me2NCH2CH2N(CH2-2-O-3,5-tBu2-C6H2)2}Cl2] (1) and [V{Me2NCH2CH2N(CH2-2-O-3,5-tBu2-C6H2)(CH2-2-O-C6H4)}Cl2] (2), were synthesised and characterized by FTIR and 1HNMR spectroscopy. Upon activation with Al(iBu)3/Ph3CB(C6F5)4, these complexes became active catalysts for 1-octene polymerization giving highly stereoregular polymers (mmmm ∼ 90%) having regioirregularly arranged units. The catalytic activity of the catalysts in ethylene homo- and copolymerization, and their ability to incorporate a comonomer were highly dependent on both the activator type and the complex structure. 1/EtAlCl2 exhibited very high activity (up to 3.3 · 107 g/(molV h)) in ethylene polymerization and produced copolymers with the highest comonomer content (up to 9.1 mol%), moderate molecular weight and narrow chemical composition distribution (CCD). Both vanadium complexes, when combined with trityl borate activator, led to ethylene copolymers with lower 1-octene content and broad CCD. In addition, the copolymers were characterized by very high molecular weight (∼1 · 106 g/mol) and narrow dispersity (Mw/Mn = 1.4–2.0).

Fractionation and thermal characteristics of biosynthesized polyhydoxyalkanoates bearing aromatic groups as side chains

Two polyhydroxyalkanoate (PHA) copolymers, poly(3-hydroxybutyrate-co-3-hydroxy-3-phenylpropioate) [P(3HB-co-3H3PhP)] and poly(3-hydroxybutyrate-co-3-hydroxy-4-phenylbutyrate) [P(3HB-co-3H4PhB)], both bearing aromatic side chains, were biosynthesized by recombinant Ralstonia eutropha fed with a respective precursor for the aromatic unit. As bacterial PHA copolymers generally exhibit broad comonomer compositional distribution, the as-biosynthesized samples, P(3HB-co-18 mol% 3H3PhP) and P(3HB-co-11 mol% 3H4PhB), were fractionated into several fractions with narrow comonomer compositional distribution using a chloroform/n-hexane mixed solvent. When the fractionated samples were aged under ambient conditions, the P(3HB-co-3H3PhP) fraction with 12 mol% 3H3PhP exhibited a melting temperature (Tm) of 132–148 °C, whereas the fractions with 15–21 mol% 3H3PhP did not exhibit melting behavior. As for P(3HB-co-3H4PhB), all fractions with a range of 4–15 mol% 3H4PhB exhibited Tm in the range 105–151 °C. The glass transition temperature (Tg) of these copolymers increased with increasing aromatic unit content, and the highest Tg of 20 °C was observed for the fraction with 21 mol% 3H3PhP. On the basis of the results presented here, the effects of aromatic comonomers on the thermal properties of the resulting copolymers are discussed. Two polyhydroxyalkanoate copolymers, poly(3-hydroxybutyrate-co-3-hydroxy-3-phenylpropioate) [P(3HB-co-3H3PhP)] and poly(3-hydroxybutyrate-co-3-hydroxy-4-phenylbutyrate) [P(3HB-co-3H4PhB)] were biosynthesized. The as-biosynthesized polymers were fractionated into several fractions with narrow comonomer compositional distribution using a chloroform/n-hexane mixed solvent. Using these fractions, the effects of aromatic comonomers on the thermal properties were investigated.

Determination of bimetallic architectures in nanometer-scale catalysts by combining molecular dynamics simulations with x-ray absorption spectroscopy.

Here we present an approach for the determination of an atomic structure of small bimetallic nanoparticles by combining extended X-ray absorption fine structure spectroscopy and classical molecular dynamics simulations based on the Sutton-Chen potential. The proposed approach is illustrated in the example of PdAu nanoparticles with ca 100 atoms and narrow size and compositional distributions. Using a direct modeling approach and no adjustable parameters, we were able to reproduce the size and shape of nanoparticles as well as the intra-particle distributions of atoms and metal mixing ratios and to explore the influence of these parameters on the local structure and dynamics in nanoparticles.

Co-Cu Nanoparticles: Synthesis by Galvanic Replacement and Phase Rearrangement during Catalytic Activation.

The control of the phase distribution in multicomponent nanomaterials is critical to optimize their catalytic performance. In this direction, while impressive advances have been achieved in the past decade in the synthesis of multicomponent nanoparticles and nanocomposites, element rearrangement during catalyst activation has been frequently overseen. Here, we present a facile galvanic replacement-based procedure to synthesize Co@Cu nanoparticles with narrow size and composition distributions. We further characterize their phase arrangement before and after catalytic activation. When oxidized at 350 °C in air to remove organics, Co@Cu core-shell nanostructures oxidize to polycrystalline CuO-Co3O4 nanoparticles with randomly distributed CuO and Co3O4 crystallites. During a posterior reduction treatment in H2 atmosphere, Cu precipitates in a metallic core and Co migrates to the nanoparticle surface to form Cu@Co core-shell nanostructures. The catalytic behavior of such Cu@Co nanoparticles supported on mesoporous silica was further analyzed toward CO2 hydrogenation in real working conditions.

Synthesis of Supported RhMo and PtMo Bimetallic Catalysts by Controlled Surface Reactions

AbstractWe previously described a synthesis method to prepare bimetallic catalysts with narrow nanoparticle size and composition distributions by means of controlled surface reactions (CSR) between a reduced supported metal nanoparticle and an organometallic precursor of an oxophilic promoter metal. Herein, we report a comparison of such catalysts with those prepared by traditional incipient wetness impregnation. STEM/EDS analysis indicates that catalysts prepared by CSR exhibit more effective interaction of metals, thereby minimizing the undesirable formation of component‐rich nanoparticles and/or monometallic domains. Reaction kinetics studies using these bimetallic catalysts reveal that optimal conversion rates in a selective CO hydrogenolysis reaction (i.e., hydrogenolysis of 2‐(hydroxymethyl)tetrahydropyran to 1,6‐hexanediol) could be achieved using a lower amount of the oxophilic promoter metal for the catalysts prepared by the CSR approach, as compared to their impregnated counterparts.

Preparation and characterization of narrow compositional distribution polyampholytes as potential biomaterials: Copolymers of N‐(3‐aminopropyl)methacrylamide hydrochloride (APM) and methacrylic acid (MAA)

ABSTRACTThis article describes the preparation and solution properties of a series of polyampholytes composed of N‐(3‐aminopropyl)methacrylamide hydrochloride (APM) and methacrylic acid (MAA). In particular, conditions were found where the copolymers could be formed with little or no drift in composition over the course of polymerization to quite high conversions. The compositional drift, common to many copolymerizations, was limited by adjusting the reactivity of MAA through control of its degree of ionization (i.e., pH). As revealed by potentiometric measurements and changes in 1H NMR spectra, the solution pH drifted over the course of some polymerizations. This was ascribed to changes in the pKa values of the ammonium and carboxylate groups upon incorporation in the copolymer. The pH drift led to a change in degree of MAA ionization, and hence the relative reactivities of APM and MAA, but this effect could be minimized by using a buffer. Precipitation, which occurred during some polymerizations, could be prevented, in some cases, by the addition of salt or an organic cosolvent. Even in cases where precipitation could not be prevented, it was found that the copolymer was still formed with minimal compositional drift. The solubility of the resulting polyampholytes in aqueous solution was found to depend on their composition, as well as pH, ionic strength and temperature. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 353–365

Comprehensive scenario for single-crystal growth and doping dependence of resistivity and anisotropic upper critical fields in (Ba1−xKx)Fe2As2(0.22≤x≤1)

Large high-quality single crystals of hole-doped iron-based superconductor (Ba$_{1-x}$K$_x$)Fe$_2$As$_2$ were grown over a broad composition range $0.22 \leq x \leq 1$ by inverted temperature gradient method. We found that high soaking temperature, fast cooling rate, and adjusted temperature window of the growth are necessary to obtain single crystals of heavily K doped crystals (0.65$\leq x \leq$ 0.92) with narrow compositional distributions as revealed by sharp superconducting transitions in magnetization measurements and close to 100% superconducting volume fraction. The crystals were extensively characterized by x-ray and compositional analysis, revealing monotonic evolution of the $c$-axis crystal lattice parameter with K substitution. Quantitative measurements of the temperature-dependent in-plane resistivity, $\rho(T)$ found doping-independent, constant within error bars, resistivity at room temperature, $\rho(300K)$, in sharp contrast with significant doping dependence in electron and isovalent substituted BaFe$_2$As$_2$ based compositions. The shape of the temperature dependent resistivity, $\rho(T)$, shows systematic doping-evolution, being close to $T^2$ in overdoped and revealing significant contribution of the $T$-linear component at optimum doping. The slope of the upper critical field, $d H_{c2}/dT$, scales linearly with $T_c$ for both $H\parallel c$, $ H_{c2,c}$, and $H \parallel ab$, $H_{c2,ab}$. The anisotropy of the upper critical field, $\gamma \equiv H_{c2,ab} / H_{c2,c}$ determined near zero-field $T_c$ increases from $\sim$2 to 4-5 with increasing K doping level from optimal $x \sim$0.4 to strongly overdoped $x$=1.

Synthesis and Characterization of Well-Controlled Isotactic Polypropylene Ionomers Containing Ammonium Ion Groups

This paper discusses the synthesis of a new family of well-controlled isotactic polypropylene ionomers (iPP-NH3+Cl–) containing up to 5 mol % of NH3+Cl– ionic groups, with high molecular weight and narrow molecular weight and composition distributions, as well as good processability in melt and solution. A systematic study was conducted using various isospecific Ziegler–Natta and metallocene catalysts in the copolymerization of propylene and a high α-olefin comonomer containing a silane-protected amino group and the subsequent work-up procedures that can prevent undesirable side reactions in forming iPP-NH3+Cl– ionomers in a one-pot process. The resulting copolymers were carefully monitored by polymer solubility and a combination of NMR, GPC-triple detectors, DSC, and mechanical property measurements. Evidently, the most suitable reaction process requires a combination of the rac-Me2Si[2-Me-4-Ph(Ind)]2ZrCl2 metallocene catalyst system with a purified d-MAO (TMA-free), 6-bis(trimethylsilyl)amino-1-hexene comonomer during the copolymerization reaction and a work-up procedure to directly interconvert the silane-protected amino groups (−N(SiMe3)2) into −NH3+Cl– ionic groups before exposing to air. The attempt of isolating both iPP-N(SiMe3)2 and iPP-NH2 intermediates resulted in the insoluble (cross-linked) products. On the other hand, the resulting iPP-NH3+Cl– ionomers were melt processed in air and showed a systematic increase of mechanical properties and high-temperature stability with the increase of NH3+Cl– content.

Versatile Lead-Free Solder Electroplating Products for Advanced Bumping Technologies

Lead-free SnAg solder bumps deposited by electroplating are used extensively in high volume production lines for a number of new bumping technologies including C4 bumps, Cu pillars capped with SnAg solder and 3D microbumps. New bumping technologies present their challenging requirements such as tightly controlled thickness uniformity, alloy composition uniformity and avoidance of reflow voids to create high yields and low defects. To meet these requirements, SnAg plating chemistry must deliver strong performance over a wide range of applications. Traditional device manufacturers, wafer foundry companies and Outsourced Assembly and Test (OSAT) companies are manufacturing a number of different types of bumped wafers in their production lines; a diverse range of die design and pattern densities, thin and thick resist film wafers, mushroom and in-via plating, and wide range of plating rate. The variety and complexity of bumping wafers have challenged SnAg plating chemistries to meet tight requirements in terms of running cost saving and high production yield. Hence, development of versatile and robust chemistries for electroplating is critical to overcome these challenges In view of all these challenges and unmet needs in the market, Dow focused its efforts on developing a brand-new additive system for SnAg plating. On the one hand, we tapped into our know-how on solder plating to establish correlations between various types of end-user requirements and experiences to fundamental electrochemistry response. On the other hand, 300mm in-house plating and process tools are leveraged to speed up the feedback process and provide pilot run data. At the end, this highly iterative approach enabled us to optimize the performance of the chemistry without sacrifice on design space. In this paper, we will discuss next generation of SnAg electroplating products capable of achieving versatile performance requirements over a wide range of applications. The bump height WID co-planarity% ((hmax-hmin)/2havg ×100) was achieved less than ±5% over the wide range of current density from 4 ASD to 12 ASD. Smooth surface morphology, narrow Ag alloy composition distribution less than ±0.2% across the 300mm wafers, and reflow void free were observed. An optimized formulation of the next generation SnAg products was successfully demonstrated plating capability on various bumping technologies such as C4 bumping, Cu pillars capped SnAg solders and micro bumps meeting plating requirements.

Functionalization of Polypropylene by the Combination of Metallocene Catalysts and Reactive Comonomers

This paper summarizes a functionalization approach that can prepare functional PP with desirable molecular structures, including functional groups, microstructures, high molecular weight, and narrow molecular weight and composition distributions. A newly‐developed catalysis technology with several designed “reactive” comonomers to circumvent the inevitable deactivation of the transition metal cationic active site by functional groups in the direct polymerization process has been applied. The reactive comonomers, containing organoborane, benzylic protons (ϕ‐CH3), and styrene moieties exhibit three essential properties, including (a) stability with the active site, (b) solubility in the polymerization media, and (c) versatility for interconversion to desirable functional groups under mild reaction conditions. With proper choice of metallocene catalysts, they resemble to high a‐olefin monomers and can be effectively incorporated into the PP structure. In addition to the interconversion of the incorporated reactive sites to the desirable functional groups in PP copolymers, some reactive sites have been also transformed into “living” radical or anionic initiators to initiate graft‐from polymerization of polar monomers to obtain PP graft copolymers.