Ammonium Hydroxide Solution Research Articles

The non equilibrium band model of silicon in TMAH and in anisotropic electrochemical alkaline etching solutions

This study presents the energy band diagram of silicon in contact with an aqueous solution of tetra-methyl ammonium hydroxide (TMAH) during the anisotropic electrochemical etch process. The band diagram is constructed from the measured open circuit potential (OCP) and the measured total band bending of the silicon at the OCP which is determined by impedance measurements. Current–voltage as well as capacitance–voltage characteristics of silicon in contact with TMAH solutions are presented. The present study emphasizes the non-equilibrium operation of the electrochemical cell even at the open circuit potential (OCP). In previous studies of the band diagram of silicon in alkaline anisotropic etch solutions, the Fermi levels of the silicon and the electrolyte are aligned at OCP. In contrast, in the present study the Fermi levels are not aligned since steady state rather than equilibrium prevails at this operation point. The value of the measured OCP is used to determine the separation between the two quasi Fermi levels. The assumptions leading to the construction of the band diagram are elaborated. The relationships between OCP, flat band voltage, passivation potentials and Fermi potentials are discussed. The predictions of the model and the effect of conductivity type, doping level, temperature and illumination are compared with experiments. The new model and methodology presented in this study is applicable to additional anisotropic alkaline etch solutions such as KOH and EDP. It is very useful for the appropriate design of the process required for electrochemical etch stop for the fabrication of membranes and controlled micromachining of silicon.

Determination of olanzapine in human breast milk by high-performance liquid chromatography with electrochemical detection

A reversed-phase high-performance liquid chromatographic–electrochemical assay was developed and validated for the quantification of olanzapine in human breast milk. The assay involved a solid-phase extraction (SPE) of olanzapine and its internal standard on a Bond Elut Certify LRC mixed-mode cartridge. After conditioning of the SPE cartridge, human milk (1 ml) was passed through the cartridge. The cartridge was washed with five separate washing steps to remove endogenous compounds, and the analytes were eluted with ethyl acetate–ammonium hydroxide (98:2, v/v) solution. The eluate was evaporated to dryness (gentle stream of nitrogen at 40°C), and the residue was dissolved in mobile phase. The extract was injected onto a YMC basic column (150 mm×4.6 mm I.D., 5 μm particle size) at a flow-rate of 1 ml/min. A mixture of 75 m M phosphate buffer, pH 7.0–acetonitrile–methanol (48:26:26, v/v/v) was used as the mobile phase. Standard curves with a lower limit of quantitation of 0.25 ng/ml of olanzapine were linear ( r 2≥0.9992) over a range of 0.25–100 ng/ml. Based on the analysis of quality control (QC) samples, the average inter-day accuracy (RE) was 99.0% with an average precision (CV) of 6.64% over the entire range. The stability of olanzapine in human milk was established after three freeze–thaw–heat cycles and storage at −70°C for 10 months. The validated method was used to measure olanzapine concentrations in human milk during a clinical trial.

Investigation of problems associated with the determination of iodine in glacial acetic acid samples using flow injection analysis-inductively coupled plasma-mass spectrometry†

Determination of iodine in glacial acetic acid is a major concern of acetic acid manufacturers and consumers. The use of ICP-MS for iodine determinations in acetic acid is hindered by memory effects that produce an elevated background signal necessitating long rinse times between samples. In this work, different analysis methods are employed in an attempt to minimize memory and matrix effects allowing for the accurate determination of iodine in glacial acetic acid using ICP-MS. Ammonium hydroxide solutions (3.7 and 7.4 M) were better at reducing the elevated iodine signal present after the introduction of an acetic acid sample than water or 0.3 M nitric acid. Memory effects were decreased when the sample was introduced by flow injection rather than constant sample aspiration. Peak areas generated by flow injection decreased significantly with increasing ammonium hydroxide concentration in the carrier solution. Iodine determinations made with 1.7 M ammonium hydroxide as the carrier solution were higher than determinations made with 3.7 M ammonium hydroxide as the carrier solution for the same samples, however, the percentage difference between the two determinations varied widely from sample to sample. All samples were analyzed by the method of standard additions in an attempt to compensate for matrix effects. This work illustrates the importance of the carrier solution in the determination of iodine in glacial acetic acid samples.Introduction

Cobalt(II) Oxide Solubility and Phase Stability in Alkaline Media at Elevated Temperatures

A platinum-lined, flowing autoclave facility was used to investigate the solubility behavior of cobalt(II) oxide (CoO) in deoxygenated ammonium and sodium hydroxide solutions between 22 and 288°C. Co(II) ion activity in aqueous solution was controlled by a hydrous Co(II) oxide when nitrogen was used for deoxygenation and by metallic cobalt when hydrogen was used. Measured cobalt solubilities are interpreted using a Co(II) ion hydroxo- and amminocomplexing model and thermodynamic functions for these equilibria were obtained from a least-squares analysis of the data. A common set of thermodynamic properties for the species Co(OH)+, Co(OH)2(aq) and Co(OH)(NH3)+ is provided to permit accurate cobalt oxide solubility calculations over broad ranges of temperature and alkalinity.

Electrochemical Behavior of Copper in Tetramethyl Ammonium Hydroxide Based Solutions

An investigation was undertaken to characterize the electrochemical behavior of copper in tetramethyl ammonium hydroxide (TMAH) based solutions. The effect of hydrogen peroxide and abrasion with a polyvinyl alcohol (PVA) brush on the corrosion of copper in alkaline solutions were characterized. Galvanic interactions between copper and tantalum in TMAH as well as in ammonium hydroxide (NH4OH) solutions were investigated. The experimental results have shown that the corrosion of copper in TMAH is lower than that in NH4OH, especially at pH values higher than 10. Even in the presence of hydrogen peroxide, TMAH corrodes copper at a lower rate than NH4OH.

SYNTHESIS AND SOME REACTIONS OF 4-AROYL-6-ARYL PYRIDAZIN-3(2H)-THIONES

4-Aroyl-3-chloro-6-aryrylpyridazines[1] (1) react with thiourea to give 4aroyl-6-arylpyri-dazin-3 (2H)-thiones (2) respectively[2–7]. The compounds 2 reacted with dimethyl sulphate, hydrazine hydrate and hydroxylamine hydrochloride to give 4-aroyl-6-aryl-3-metylthiopyri-dazines 5, pyrazolinopyridazines 7 and isoxazolopyridazine 8, respectively. The compounds 2a-c reacted in alkaline ammonium hydroxide solution with sodium hypochlorite solution to give the isothiazolopyridazines 10a-c.

A positive-working photosensitive alkaline-developable polyimide with a highly dimensional stability and low dielectric constant based on poly(amic acid) as a polyimide precursor and diazonaphthoquinone as a photosensitive compound

A positive-working photosensitive polyimide precursor based on fluorinated poly(amic acid) (FPAA) and 2,3,4-tris(1.-oxo-2-diazonaphthoquinon-4-ylsulfonyloxy-)benzophenone (D4SB) as a photosensitive compound has been developed. FPAA was prepared by ring-opening polyaddition of dianhydrides, pyromellitic dianhydride and biphenyltetracarboxylic dianhydride, with diamine, 2,2'-bis(trifluoromethyl)benzidine, in methanol. The FPAA film showed excellent transparency to UV light and good solubility in a wide range of organic solvents. The dissolution behavior of FPAA containing 30 wt % D4SB after exposure was studied, and it was found that the difference of dissolution rate between exposed and unexposed parts was enough to get high contrast due to the photochemical reaction of D4SB in the polymer film. The photosensitive fluorinated polyimide (FPI) precursor containing 30 wt % D4SB showed a sensitivity of 80 mJ cm 2 and a contrast of 7.8 with 365 nm light when it was developed with 0.3% aqueous tetramethyl ammonium hydroxide solution at room temperature. The FPI film cured up to 360°C had a low coefficient of thermal expansion of 10.3 ppm °C 1 and a low dielectric constant of 3.04.

An ultrafine barium ferrite powder of high coercivity from water-in-oil microemulsion

An ultrafine barium ferrite powder of high coercivity and high saturation magnetization has been successfully prepared from an inverse water-in-oil microemulsion consisting of cyclohexane, NP5/NP9, and an aqueous solution of mixed ferric nitrate and barium nitrate. An ammonium hydroxide solution was used as the precipitant to obtain the hydroxide precursor of particle size in the range of 10–30 nm from the microemulsion. The resulting precursor is characterized using techniques such as thermogravimetric analysis (TGA), differential thermal analysis (DTA) and a FT-IR analyzer. It was then calcined at various temperatures ranging from 600 to 950°C in order to develop the designed barium ferrite phase. Phase development in the precursor at each calcination temperature was monitored using X-ray diffractometer and a 57Fe-Mössbauer spectrometer analyzer. The particle size and size distribution of the calcined powders were determined using light scattering technique, scanning electron microscope and a transmission electron microscope. A high purity barium ferrite was obtained when the precursor was calcined at 950°C for 4 h. It exhibits an intrinsic coercivity ( i H c) of 5639 Oe and a saturation magnetization ( M s) of 69.7 emu/g, when characterized using a vibrating sample magnetometer (VSM).

Optimization of the Cleavage Reaction for Cyanylated Cysteinyl Proteins for Efficient and Simplified Mass Mapping

Peptide chains can be cleaved selectively on the N-terminal side of cysteine residues after cyanylation of sulfhydryl groups to form an amino-terminal peptide and a series of 2-iminothiazolidine-4-carboxyl peptides. This paper describes a systematic study that was carried out to elucidate the effects of peptide structure and reaction conditions on the kinetics of the reactions and the yields of cleavage products. Both cleavage and β-elimination reactions under different conditions (pH 8.0, 9.0, and 12.0 and 1 M ammonia solution) were quantitatively evaluated using reversed-phase HPLC and matrix-assisted laser desorption/ionization-MS. Contrary to previous reports, our results showed that higher pH greatly accelerates both cleavage and β-elimination reactions, while the relative yield of β-elimination products does not increase for most of the peptides studied. Optimal results were obtained in 1 M ammonium hydroxide solution, in which cleavage is complete within an hour at ambient temperature. This improvement also minimizes side reactions otherwise associated with long hours of exposure to alkaline conditions, [original report called for 12 to 80 h of incubation in mildly alkaline (pH 8–9) buffer]. The yields of cleavage reactions depend primarily on the structure of amino acids on the N-terminal side of cyanylated cysteines; the Pro–Cys and Tyr–Cys bonds were resistant to cleavage, promoting β-elimination as the main reaction. The improved cleavage conditions greatly simplify the analytical procedure, which has been successfully applied to the determination of cysteine status in spinach ferredoxin, ovalbumin, and rabbit muscle creatine phosphokinase.

Development of an iron oxide-impregnated paper strip technique for the determination of bioavailable phosphorus in runoff

Bioavailable phosphorus (P) requires separate analysis because it is independent of physical and chemical P fractions present in runoff. Iron oxide-impregnated paper strips (P i-strips) provide a simple technique for determining bioavailable P in aqueous samples. In this study, some controversial strip preparation procedures were examined and subsequently modified, and the efficiency of the technique was compared to the conventional physico-chemical fractionation approach. P i-strips prepared using Whatman 50 filter paper rapidly drawn through iron chloride solution then immersed in ammonium hydroxide solution produced the most accurate and precise results. A strong asymptotic relationship between P uptake and the duration of shaking, coupled with rapid intra-sample transformations between P fractions, indicated that shaking for 8 h was sufficient for complete P uptake from natural water samples and standard solutions (0–250 μg P l −1). A single P i-strip was used because multiple strips increased analytical error. The contribution to P i-strips from adhering sediment particles was negligible for samples with low concentrations of solids but turbid samples (>0.75 mg l −1 suspended solids) were noticeably influenced by P derived from particulate material. Fractionation of agricultural runoff demonstrated a strong relationship between the dissolved inorganic (MRP and P i-strip fraction, but only 85% of the total dissolved fraction (TDP) was retained by the P i-strip, suggesting not all soluble P was available for biological uptake.

Solubility and phase behavior of Cr(III) oxides in alkaline media at elevated temperatures

A platinum-lined, flowing autoclave facility is used to investigate the solubility behavior of Cr2O3 and FeCr2O4 in alkaline sodium phosphate, sodium hydroxide, and ammonium hydroxide solutions between 21 and 288°C. Baseline Cr(III) ion solubilities were found to be on the order of 0.1 nmolal, which were enhanced by the formation of anionic hydroxo and phosphato complexes. At temperatures below 51°C, the activity of Cr(III) ions in aqueous solution is controlled by a Cr(OH)3·3H2O solid phase rather than Cr2O3; above 51°C the saturating solid phase is γ-CrOOH. Measured chromium solubilities were interpreted via a Cr(III) ion hydrolysis/complexing model and thermodynamic functions for the hydrolysis/complexing reaction equilibria were obtained from least-squares analyses of the data. The existence of four new Cr(III) ion complexes is reported: Cr(OH)3(H2PO4)−, Cr(OH)3(HPO4)2−, Cr(OH)3(PO4)3−, and Cr(OH)4(HPO4)-(H2PO4)4−. The last species is the dominant Cr(III) ion complex in concentrated, alkaline phosphate solutions at elevated temperatures.

Formation and Characterization of Indium Hydroxide Films

Formation and characterization of thin films of indium hydroxide, In(OH)3⋅nH2O were carried out. The indium hydroxide sample was prepared in the gel form via the reaction of indium nitrate solution with ammonium hydroxide solution. After the precipitated gel was extracted using a centrifugal separator, the gel was dispersed in deionized water for several days to prepare a colloidal solution. Films dip-coated on glass substrates were heated at several temperatures. Thin films were characterized by means of XRD, SEM, AFM, thickness measurement, TG-DTA and conductivity measurement. Although only one weak peak of the (200) plane was observed in XRD patterns, the thin films could be regarded as almost amorphous. Surfaces of all the samples were found to be smooth with roughness Rmax=7nm, and the thickness of each film was about 40nm. Depending on both the heat-treatment temperature of thin films and the relative humidity, the conductivity varied in the range of 10-7-10-3S/cm at room temperature. In addition, the conductivity measured along the surface of the sample was on the order of 10-6S/cm which was comparable with the value measured in the direction perpendicular to the surface. These results suggested that the carriers of conduction were protons based on water incorporated in the crystallographic channels and grain boundaries of the thin films.

Seeding effect in hydrothermal synthesis of nanosize yttria

Nanoscale particles are of interest in fundamental as well as applied research because many properties of materials change drastically when the crystallite size reaches the nano=submicrometer range [1]. Since nanoscale particles have relatively large surface areas, they tend to agglomerate to minimize the total surface energy. Agglomeration adversely affects their properties. One approach to make nanoscale particles without agglomeration involves the use of surfactant molecules during the synthesis stage [2]. The surfactant molecules adsorb on the surface of particles and stabilize the particle against agglomeration by either electrostatic repulsion or steric force [3]. This is one of the chemical approaches to control the particle size. It has been demonstrated that the physical properties, especially particle size and surface area of ceramic powders can be altered by adopting a combination of two processes, namely coprecipitation and hydrothermal. Beidellite Na0:4 Al2(Si3:6Al0:4)O10(OH)2 4H2O has been synthesized by a combination of sol-gel and hydrothermal processes, in which an ideal beidellite composition was prepared from either tetra ethyl orthosilicate (TEOS) [4] or colloidal silica [5]. Yanazisawa et al. [6] used the combination of coprecipitation and hydrothermal methods to obtain beidellite at a lower temperature without agglomeration. Recently, it has been reported that the formation of many transition metal oxides, e.g., Fe3O4, Fe2O3 and a-Al2O3 may be controlled by nucleating or ` seeding'' with, e.g., CuO, SiO2 and a-Al2O3, respectively [7±9]. Applying the seeding effect in order to enhance transformation kinetics and to control the development of a desired phase has been successfully investigated [9±11]. However, to our knowledge it has not been applied to yttria or doped yttria. The aim of this paper is to report the preparation of nanoscale yttria by a combined method of coprecipitation and hydrothermal processes in the presence of a seed. The coprecipitation method was employed to produce a gel in the presence of modi®er (a mixture of tween-80 and â-alanine). Seeds of Y2O3 were added to the coprecipitated gel. The gel was then subjected to a hydrothermal treatment. This study showed that the seeding not only represents a unique method to obtain nanosize yttria but also prevents the formation of hydroxide during the course of hydrothermal treatment. However, the seeding effect was found to be selective of the precursor of yttria. A precursor solution was prepared by dissolving a known amount of precursor salt (Y(NO3)3 5H2O or YCl3 4H2O) in water and stirring for 2 h. The modi®er solution was prepared by dissolving 10% wt=wt of the surface modi®er with respect to Y2O3 in 50 ml of an aqueous ammonium hydroxide solution (pH . 10) and stirring for an hour at room temperature. The precursor solution was then added to the modi®er solution drop-by-drop through a burette at a controlled rate (10 drops per minute) with vigorous stirring. Seeds of 4% wt=wt of Y2O3 particles were added to the gel. The hydrothermal treatment of the gel was carried out at 190 8C for 1, 2 and 4 h in a 300 cm stainless steel autoclave lined with Te on (Bergohof GmbH, Labortechnik; DAH904, Germany). The pressure inside the autoclave was not controlled. However, the autoclave was tight and it is felt that the pressure corresponded to the autogenous water vapour pressure. The resulting powder was washed by 20% acetic acid solution in water and dried in an oven at 60 8C for 24 h. The bulk density of the material was measured using a Micromeritics densitometer (Accu Pyc 1330). The infrared spectra of the samples were recorded on a Fourier transform infrared spectrometer (Brucker, IFS 25). The surface area was measured by applying multipoint Brunauer±Emmett±Teller (BET) for all samples with a minimum of 5 points on a Micrometrics Unit (ASAP 2400). Powders were degassed at 150 8C before surface area measurements. The crystalline phase was determined by powder X-ray diffraction (XRD) on a D-500 Siemens powder diffractometer. The microstructure of particles was investigated in a high resolution transmission electron microscope (HRTEM) (Philips, CM 200, FEG) operated at 200 kV with a line resolution of 0.14 nm. For the preparation of the TEM specimen, the powder was heavily diluted with acetone, partially deagglomerated by ultrasonic

Low‐Temperature Electrochemical Synthesis of ZrO2 Films on Zirconium Substrates: Deposition of Thick Amorphous Films and in situ Crystallization on Zirconium Anode

The feasibility of synthesizing crystalline ZrO2 films at low temperatures was evaluated using an electrochemical method. Anodization of zirconium‐metal substrates in tetraethyl ammonium hydroxide (TEAOH) solutions under constant applied voltage conditions at ∼25° and ∼100°C was investigated. The chemistry and microstructure of the anodic oxide films deposited on the zirconium‐metal substrates under the above conditions were characterized using X‐ray diffractometry and scanning electron microscopy. The results indicated that, with sufficiently high applied voltages (in the range of 300 V) at pH ∼9.5, the initial dissolution of the zirconium anode resulted in the local saturation of the electrolyte solution with Zr4+, forming Zr(OH)−5, which deposited electrophoretically on the anode as a thick, gelatinous film at 25°C. Similar treatments at 100°C resulted in an in situ crystallization of Zr(OH)4 gel to monoclinic ZrO2.

The shrinking dollar bill

Everyone knows that the value of the dollar bill decreases each year, but there is actually a way of demonstrating a shrinking dollar. This demonstration can also be done with any other item made from paper, such as foreign currency, parking tickets, memos from your boss, or writing paper.Caution: The entire demonstration must be done in a hood. Wear goggles, protective gloves, and protective clothing. In the hood, fill a large Dewar flask or beaker halfway with liquid ammonia from an ammonia tank. (Ammonium hydroxide solution does not work.) Soak a dollar bill in the ammonia for a few seconds; then, using tongs, remove the dollar bill and allow the ammonia to evaporate from it in the hood. As the ammonia evaporates, the dollar bill shrinks. This process can be repeated several times to shrink the bill even more. To obtain an unwrinkled dollar bill, place the wet bill between two metal blocks and heat the blocks with a heat gun until the bill dries.We weighed the dollar bill before and after the process and found no change in mass. The smallest bill obtained measured of 9.8 cm by 4.8 cm. A normal dollar bill has dimensions of 15.7 cm by 6.6 cm.The chemistry of this demonstration is unknown at this time. Suggested explanations will be welcome.

The wash-off of reactive dyes on cellulosic fibres. Part 4: The use of different alkalis with monochlorotriazinyl dyes on cotton

One monochlorotriazinyl and two bis-monochlorotriazinyl dyes were applied to cotton fabric and the dyeings then washed-off using aqueous solutions of ammonium hydroxide, sodium bicarbonate, potassium hydroxide, sodium hydroxide or five buffer systems. The effects of varying the amount of each alkali used on both the extent of dye removal and the wash fastness of the dyeings were determined. It was found that potassium hydroxide and sodium bicarbonate were more effective than the two other alkalis used and, also, that the buffer systems were less effective than the alkalis in removing dye. The level of wash-fastness achieved was generally independent of the wash-off method used.

Determination of a cyclic hexapeptide (L-743 872), a novel pneumocandin antifungal agent in human plasma and urine by high-performance liquid chromatography with fluorescence detection

A method based on high-performance liquid chromatography (HPLC) with fluorescence detection for the determination of a novel peptide antifungal agent, L-743 872 (I), in human plasma and urine is presented. Drug and internal standard were extracted from plasma and urine using diol solid-phase extraction columns and selectively eluted using a solution of trifluroacetic acid and ammonium hydroxide in methanol. Chromatography was performed on a wide pore C8 column and detection was by fluorescence. Loss of drug from urine due to adsorption to plastic surfaces was prevented by the addition of bovine serum albumin (0.5% final concentration). The range of the standard line was 10 to 1000 ng/ml for both matrices. The recovery of drug from plasma and urine was 76% and 84%, respectively. The assay was used to measure drug concentrations in human plasma and urine after the administration of intravenous (IV) doses of I.

High performance liquid chromatographic determination of folic acid and its photodegradation products in the presence of riboflavin

A high performance liquid chromatographic procedure was developed to determine folic acid and its photodegradation products, p-aminobenzoic acid, pterine-6-carboxylic acid, p- aminobenzoyl- l-glutamic acid, and pteroic acid in the presence of riboflavin. The method involves reversed phase, paired-ion chromatography on μ-BondaPak C 18 column using a UV detector (254 nm), and isocratic solvent system (at ambient temperature) comprising 0.017 M monobasic potassium phosphate, tetrabutyl ammonium hydroxide solution (20%, aqueous) and methanol (870:15:250, v/v). The range of quantitation for the individual compounds was found to be: p-aminobenzoic acid, 0.01–1.25 × 10 −5 M; pterine-6-carboxylic acid, 0.01–2.0 × 10 −5 M; p- aminobenzoyl- l-glutamic acid, 0.02–2.0 × 10 −5 M; pteroic acid, 0.02–2.5 × 10 −5 M; folic acid, 1.0–5.0 × 10 −5 M; riboflavin, 1.0–5.0 × 10 −5 M. Linear regression analysis of the data demonstrates adequate performance of the method in terms of accuracy and precision (R.S.D. 3%). The method is specific, rapid and convenient and has been applied to photodegradation studies of folic acid in the presence and absence of riboflavin.

The molecular basis of fracture in crosslinked glassy polymers

Crosslinked polystyrene (XPS) and poly(methyl methacrylate) (XPMMA) were prepared by photopolymerization of the respective monomers in the presence of reversible crosslinkers, acrylic acid anhydride (AAA), and methacrylic acid anhydride (MAA). Fracture studies on the crosslinked samples were carried out using a Dental Burr Grinding Instrument (DBGI). The fracture energy in all cases showed a maximum around 1.5–5.0 mol % crosslinker. The samples were decrosslinked by hydrolysis using dilute aqueous ammonium hydroxide solutions to determine the number of chain scissions as a result of grinding. The number of chain scissions increased asymptotically with crosslink density in the range of a 0.0–10.0 mol % crosslinker. The number of bonds activated per scission, obtained from the calculated total chain scission energy (after subtracting the chain pullout energy) and the experimental number of chain scissions, remained fairly constant for AAA-PS and AAA-PMMA at 312 ± 150 bonds and 202 ±50 bonds, respectively, in the region below the fracture energy maximum. In an attempt to explain the fracture energy increases, increasing physical entanglements with crosslinking is considered. © 1997 John Wiley & Sons, Inc. J Appl Polm Sci 65:1001–1011, 1997

The molecular basis of fracture in crosslinked glassy polymers

Crosslinked polystyrene (XPS) and poly(methyl methacrylate) (XPMMA) were prepared by photopolymerization of the respective monomers in the presence of reversible crosslinkers, acrylic acid anhydride (AAA), and methacrylic acid anhydride (MAA). Fracture studies on the crosslinked samples were carried out using a Dental Burr Grinding Instrument (DBGI). The fracture energy in all cases showed a maximum around 1.5-5.0 mol % crosslinker. The samples were decrosslinked by hydrolysis using dilute aqueous ammonium hydroxide solutions to determine the number of chain scissions as a result of grinding. The number of chain scissions increased asymptotically with crosslink density in the range of a 0.0-10.0 mol % crosslinker. The number of bonds activated per scission, obtained from the calculated total chain scission energy (after subtracting the chain pullout energy) and the experimental number of chain scissions, remained fairly constant for AAA-PS and AAA-PMMA at 312 ± 150 bonds and 202 ± 50 bonds, respectively, in the region below the fracture energy maximum. In an attempt to explain the fracture energy increases, increasing physical entanglements with crosslinking is considered.