Length scale hierarchy in sol,gel, and coacervate phases of gelatin

Length scale hierarchy in gelatin sol, gel, and coacervate (induced by ethanol) phases, having same concentration of gelatin in aqueous medium (13% w/v), has been investigated through small angle neutron scattering and rheology measurements. The static structure factor profile, I(q) versus wave vector q, was found to be remarkably similar for all these samples. This data could be split into three distinct q‐regimes: the low‐q regime, I_ex(q) = I_ex(0)/(1+q²ζ²)² valid for q < 3R_g^?1; the intermediate q‐regime, I(q) = I(0)/(1+q²ξ²) for 3R_g^?1 < q < ξ^?1; and the asymptotic regime, I(q) = (c/q) exp(?R_c²q²/2) for q > ξ^?1. Consequently, three distinct length scales could be deduced from structure factor data: (a) inhomogeneity of size, ζ = 20 ± 1 nm for all the three phases; (b) average mesh size, ξ₀ = 2.6 ± 0.2 nm for sol and gel, and smaller mesh size, ξ_os = 1.2 ± 0.2 nm for coacervate; and (c) cross section of gelatin chains, R_c = 0.35 ± 0.04 nm. In addition, the structure factor data obtained from coacervating solution analyzed in the Guinier region, I(q) = exp(?q²R_g²/3), yielded value of typical radius of gyration of clusters, R_g ≈ 69 nm that indicated existence of triple‐helices of length, L ≈ 239 nm; (d) Frequency and temperature sweep measurements conducted on coacervate samples revealed two other length scales: (e) viscoelastic length, ξ_ve = 14 ± 2 nm and (f) correlation length at melting, ξ_T = 500 ± 70 nm. Thus, existence of six distinct length scales, (a–f), ranging from 1.2 to 500 nm has been established in the coacervate phase of gelatin–ethanol–water system. Results are discussed within the framework of Landau‐Ginzburg treatment of dynamically asymmetric systems (Prog Theor Phys 1977, 57, 826; Phys Rev A 1991, 44, R817; J Phys II (France) 1992, 2, 1631). © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1653–1667, 2006     

Non‐linear dynamics of spinodal decomposition

A new approach is proposed to describe the spinodal decomposition, in particular, in polymer binary blends. In the framework of this approach, the spinodal decomposition is described as a relaxation of one‐time structure factor S(q,t) treated as an independent dynamic object (a peculiar two‐point order parameter). The dynamic equation for S(q,t), including the explicit expression for the corresponding effective kinetic coefficient, is derived. In the first approximation this equation is identical to the Langer equation. We first solved it both in terms of higher transcendental functions and numerically. The asymptotic behaviour of S(q,t) at large (from the onset of spinodal decomposition) times is analytically described. The values obtained for the power‐law growth exponent for the large‐time peak value and position of S(q,t) are in good agreement with experimental data and results of numerical integration of the Cahn‐Hilliard equation.     

Phase separation of off‐critical polymer blends of poly(styrene‐co‐maleic anhydride) and poly(methyl methacrylate). I. Kinetics of spinodal decomposition

The kinetics of phase separation via the spinodal decomposition of poly(styrene‐co‐maleic anhydride)/poly(methyl methacrylate) from a delay time period to late stages were investigated with a light scattering technique. The standard procedure for identifying four stages of spinodal decomposition, based on the characteristics of concentration fluctuations, was clearly introduced with the light scattering method. The spinodal limits were divided into four stages: the delay time, the early stage, the intermediate stage, and the late stage. The validity of the linearized theory was reviewed because it was used as an indicator of the limit of the early stage of spinodal decomposition, which divided the delay time period from the early stage and the early stage from the intermediate stage. The linearized theory fit the experimental results very well after the delay time. The scaled structure function of the melt‐mixed blend was analyzed. The universality of the scale structure function, F(x) = S(q,t)q_m³(t) (where S is the structure function, x is equal to q/q_m, q is the scattering wave vector, q_m is the maximum wave vector, and t is the time in seconds), indicated the late stage of phase separation and divided the late stage from the intermediate stage. The simple normalized scaling function profile for the cluster region proposed by Furukawa described the experimental data very well, whereas the profile for deep quenching, which was recently suggested, showed some discrepancies. As a result of the phase separation, the processing of this blend may be able to be developed to provide the most suitable morphology. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 871–885, 2004     

Phase separation in mixtures of poly(ethylene glycol monomethylether) and poly(propylene glycol) oligomers

Time-resolved light scattering was employed to investigate kinetics of phase separation in mixtures of poly (ethylene glycol monomethylether) (PEGE)/poly (propylene glycol) (PPG) oligomers. Phase diagrams for PEGE/PPG of varying molecular weights were established by means of cold point measurements. The oligomer mixtures reveal an upper critical solution temperature (UCST). Several temperature quench experiments were carried out with a 60/40 PEGE/PPG blend by rapidly quenching from a single phase (69°C) to two-phase temperatures (66–61°C) at 1°C intervals. As is typical for oligomer mixtures, the early stage of spinodal decomposition (SD) was not detected. The kinetics of phase decomposition was found to be dominated by the late stage of SD. Time-evolution of scattering intensity was analyzed in accordance with nonlinear and dynamical scaling theories. The time dependence of the peak intensity I_m and the corresponding peak wavenumber q_m was found to follow the power-law {I_m(t)? t^α, q_m(t)? t^-β} with the values of α = 3 ± 0.3 and β = 1 ± 0.2, which are very close to the values predicted by Siggia. This process has been attributed to a coarsening mechanism driven by surface tension. In the temporal scaling analysis, the structure function reveals university with time, suggesting self-similarity. Phase separation dynamics in 60/40 PEGE/PPG resembles the behavior predicted for off-critical mixtures.     

Kinetics of the droplet formation at the early and intermediate stages of the spinodal decomposition in homopolymer blends

The kinetics of the droplet formation during the spinodal decomposition (SD) of the homopolymer blends has been studied by numerical integration of the Cahn‐Hilliard‐Cook equation. We have found that the droplet formation and growth occurs when the minority phase volume fraction, f_m , approaches the percolation threshold value, f_thr = 0.3 ± 0.01. The time for the formation of the disperse droplet morphology (coarsening time) depends only on the equilibrium minority phase volume fraction, f_m . f_m approaches its equilibrium value logarithmically at the late SD stages, and, therefore, the coarsening time decreases exponentially as the average volume fraction or the quench depth decrease. Since the temporal evolution of the total interfacial area does not depend on the quench conditions and blend morphology, the average droplet size and the droplet number density is determined by the coarsening time. Within the time scale studied, the droplet number density decreases with time as t ^{–0.63±0.03}; the average mean curvature decreases as t ^{–0.35±0.05}; the average Gaussian curvature decreases as t ^{–0.42±0.03}, and the average droplet compactness ˜V/S^3/2 where S is the surface area and V is the volume) approaches a spherical limit logarithmically with time. The droplets with larger area have lower compactness and in the low compactness limit their area is a parabolic function of compactness. The size and shape distribution functions have been also investigated.     

Phase Behavior and Morphology of Poly(Methyl Methacrylate)/Poly(α‐Methyl Styrene‐co‐Acrylonitrile) Blends Under Quiescent and Shear Flow

The kinetics of spinodal decomposition (SD) for the binary blend poly(methyl methacrylate), PMMA, and Poly(α‐methylstyrene‐co‐acrylonitrile), PαMSAN, with 31 wt% AN content (LCST‐type phase diagram) has been thoroughly studied using a time‐resolved light scattering technique. The early stage SD was dominated by a diffusion process and can be well described within the framework of the linearized Cahn‐Hilliard theory. The spinodal temperature could be evaluated from the analysis of the early stage SD based on the Cahn theory. In addition, viscoelastic properties of this system have been systematically investigated at temperatures below and above the LCST phase diagram. The linear viscoelastic properties of the blends were found to be greatly changed by phase separation in the two‐phase regime. This change in the linear viscoelastic properties attributed to an additional contribution of concentration fluctuations to the material functions at the phase separation temperatures. The phase diagram of the blends was also estimated rheologically through the dynamic temperature ramps of G′, G″ and η*. Furthermore, the phase behavior and morphology of this system has been studied under different shear rates using simple shear apparatus and transmission electron microscopy (TEM), respectively.     

Investigation on LCST behavior of a new amorphous/crystalline polymer blend: Poly(n‐methyl methacrylimide)/poly(vinylidene fluoride)

The liquid–liquid phase‐separation (LLPS) behavior of poly(n‐methyl methacrylimide)/poly(vinylidene fluoride) (PMMI/PVDF) blend was studied by using small‐angle laser light scattering (SALLS) and phase contrast microscopy (PCM). The cloud point (T_c) of PMMI/PVDF blend was obtained using SALLS at the heating rate of 1 °C min^?1 and it was found that PMMI/PVDF exhibited a low critical solution temperature (LCST) behavior similar to that of PMMA/PVDF. Moreover, T_c of PMMI/PVDF is higher than its melting temperature (T_m) and a large temperature gap between T_c and T_m exists. At the early phase‐separation stage, the apparent diffusion coefficient (D_app) and the product (2Mk) of the molecules mobility coefficient (M) and the energy gradient coefficient (k) arising from contributions of composition gradient to the energy for PMMI/PVDF (50/50 wt) blend were calculated on the basis of linearized Cahn‐Hilliard‐Cook theory. The kinetic results showed that LLPS of PMMI/PVDF blends followed the spinodal decomposition (SD) mechanism. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1923–1931, 2008     

Neutral polymer slow mode and its rheological correlate

Quasi‐elastic light scattering spectroscopy intensity–intensity autocorrelation functions [S(k,t)] and static light scattering intensities of 1 MDa hydroxypropylcellulose in aqueous solutions were measured. With increasing polymer concentration, over a narrow concentration range, S(k,t) gained a slow relaxation. The transition concentration for the appearance of the slow mode (c^t) was also the transition concentration for the solution‐like/melt‐like rheological transition (c⁺) at which the solution shear viscosity [η_p(c)] passed over from a stretched exponential to a power‐law concentration dependence. To a good approximation, we found c^t[η] ≈ c⁺[η] ≈ 4, [η] being the intrinsic viscosity. The appearance of the slow mode did not change the light scattering intensity (I): from a concentration lower than c^t to a concentration greater than c^t, I/c fell uniformly with increasing concentration. The slow mode thus did not arise from the formation of compact aggregates of polymer chains. If the polymer slow mode arose from long‐lived structures that were not concentration fluctuations, the structures involved much of the dissolved polymer. At 25 °C, the mean relaxation rate of the slow mode approximately matched the relaxation rate for the diffusion of 0.2‐μm‐diameter optical probes observed with the same scattering vector. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 323–333, 2005     

Equations of state for polyamide‐6 and its nanocomposites. 1. Fundamentals and the matrix

The pressure‐volume‐temperature (PVT) surface of polyamide‐6 (PA‐6) was determined in the range of temperature T = 300–600 K and pressure P = 0.1–190 MPa. The data were analyzed separately for the molten and the noncrystalline phase using the Simha‐Somcynsky (S‐S) equation of state (eos) based on the cell‐hole theory. At T_g(P) ≤ T ≤ T_m(P), the “solid” state comprises liquid phase with crystals dispersed in it. The PVT behavior of the latter phase was described using Midha‐Nanda‐Simha‐Jain (MNSJ) eos based on the cell theory. The data fitting to these two theories yielded two sets of the Lennard‐Jones interaction parameters: ε*(S‐S) = 34.0 ± 0.3 and ε*(MNSJ) = 22.8 ± 0.3 kJ/mol, whereas v*(S‐S) = 32.00 ± 0.1 and v*(MNSJ) = 27.9 ± 0.2 mL/mol. The raw PVT data were numerically differentiated to obtain the thermal expansion and compressibility coefficients, α and κ, respectively. At constant P, κ followed the same dependence on both sides of the melting zone near T_m. By contrast, α = α(T) dependencies were dramatically different for the solid and molten phase; at T < T_m, α linearly increased with increasing T, then within the melting zone, its value step‐wise decreased, to slowly increase at higher temperatures. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 299–313, 2009     

Light scattering and image analysis studies in polymer blends

Various optical techniques have been investigated as potential candidates for characterization of multiphase polymeric materials. The model calculations and corresponding experiments (time‐resolved light scattering and image analysis) have been conducted to investigate the kinetics of phase dissolution of polymer blends. The blends studied were polystyrene/poly (methyl methacrylate) mixtures with diblock copolymer composed of the corresponding homopolymers. The time evolution of the spinodal peak position q_m(t,T) and the scattered intensity maximum I_m(t,T) at q_m have been compared with theoretically predicted values of exponents for distinct time scales of the phase dissolution in various temperature regimes.     

Gelation Studies: Comparison of the Critical Exponents Obtained by Dynamic Light Scattering and Rheology, 2

Summary: The sol–gel transition of two thermoreversible gelling mixtures made of xanthan gum and locust‐bean gum has been studied by using in situ, time‐resolved dynamic light scattering (DLS) and in situ rheology. A critical dynamical behavior was observed near the sol–gel transition, which was characterized by the presence of power‐law spectra over three and four decades in the time‐intensity correlation function g₂(t) − 1 ∼ t^−μ and over four and three decades in the oscillatory shear experiment G′(ω) ∼ G″(ω) ∼ ωⁿ. A comparison of the critical exponents obtained (μ₁ ≈ 0.36, μ₂ ≈ 0.32 and n₁ ≈ 0.62, n₂ ≈ 0.67) was made as a function of the dependence of the two mixing ratios according to the theory by Doi and Onuki. New experiments were also performed to compare the critical exponents on such a thermoreversible system.

Double‐logarithmic plot of the time‐intensity correlation functions g₂(t) − 1 versus the delay time, t, at a 90° scattering angle and at several temperatures of the mixture 1.     

The Equilibrium Partial Pressure of HgI2 over and Thermodynamic Properties of Hg3Te2I2 1)

The high temperature vaporization pattern of Hg₃Te₂I₂(s,l) shows four distinctly different regimes, similar to those of the HgTe vaporization. The most predominant species in the vapor phase in all four regimes is HgI₂(g), followed by Hg(g) and, possibly, Te₂I₂(g). The width of the “homogeneity range” of Hg₃Te₂I₂(s) was determined to be less than about 0.17 mole‐% HgI₂. Applying the second‐law method to the vaporization of HgTe‐saturated Hg₃Te₂I₂(s) at higher temperatures yields the heat and entropy of vaporization of 20.9 ± 2.3 (kcal/mole) and of 27.5 ± 2.8 (cal/mole K), respectively, with estimated total uncertainties of less than ± 5.8 (kcal/mole) and ± 7.6 (cal/mole K), at an average temperature of 722 K. With an estimated heat capacity function of Hg₃Te₂I₂(s) and estimated thermodynamic values for HgI₂‐saturated HgTe(s), the heat of formation and absolute entropy of Hg₃Te₂I₂(s) are computed to be = ?49.7 ± 1.1 (kcal/mole) and = 97.3 ± 1.4 (cal/mole K), with estimated total uncertainties of ± 8.3 (kcal/mole) and ± 14.0 (cal/mole K). The combined results of this investigation provide valuable information for the crystal growth of this material from the vapor and molten phase.     

Kinetic and Mechanisms of the Homogeneous,Unimolecular Elimination of Phenyl Chloroformate and p‐Tolyl Chloroformate in the Gas Phase

The gas‐phase elimination of phenyl chloroformate gives chlorobenzene, 2‐chlorophenol, CO₂, and CO, whereasp‐tolyl chloroformate produces p‐chlorotoluene and 2‐chloro‐4‐methylphenol CO₂ and CO. The kinetic determination of phenyl chloroformate (440–480^oC, 60–110 Torr) and p‐tolyl chloroformate (430–480°C, 60–137 Torr) carried out in a deactivated static vessel, with the free radical inhibitor toluene always present, is homogeneous, unimolecular and follows a first‐order rate law. The rate coefficient is expressed by the following Arrhenius equations: Phenyl chloroformate: Formation of chlorobenzene, log k_I = (14.85 ± 0.38) – (260.4 ± 5.4) kJ mol^?1 (2.303RT)^?1; r = 0.9993 Formation of 2‐chlorophenol, log k_II = (12.76 ± 0.40) – (237.4 ± 5.6) kJ mol^?1(2.303RT)^?1; r = 0.9993 p‐Tolyl chloroformate: Formation of p‐chlorotoluene: log k_I = (14.35 ± 0.28) – (252.0 ± 1.5) kJ mol^–1 (2.303RT)^?1; r = 0.9993 Formation of 2‐chloro‐4‐methylphenol, log k_II = (12.81 ± 0.16) – (222.2 ± 0.9) kJ mol^?1(2.303RT)^–1; r = 0.9995 The estimation of the k_I values, which is the decarboxylation process in both substrates, suggests a mechanism involving an intramolecular nucleophilic displacement of the chlorine atom through a semipolar, concerted four‐membered cyclic transition state structure; whereas the k_II values, the decarbonylation in both substrates, imply an unusual migration of the chlorine atom to the aromatic ring through a semipolar, concerted five‐membered cyclic transition state type of mechanism. The bond polarization of the C–Cl, in the sense C^{δ+ …} Cl^δ?, appears to be the rate‐determining step of these elimination reactions.     

Unusual finite size effects in the Monte Carlo simulation of microphase formation of block copolymer melts

Extensive Monte Carlo simulations are presented for the Fried-Binder model of block copolymer melts, where polymer chains are represented as self and mutually avoiding walks on a simple cubic lattice, and monomer units of different kind (A, B) repel each other if they are nearest neighbors (ε_AB > 0). Choosing a chain length N = 20, vacancy concentration Φ_v = 0,2, composition ƒ = 3/4, and a L × L × L geometry with periodic boundary conditions and 8 ≤ L ≤ 32, finite size effects on the collective structure factor S(q) and the gyration radii are investigated. It is shown that already above the microphase separation transition, namely when the correlation length ξ(T) of concentration fluctuations becomes comparable with L, a nonmonotonic variation of both S(q) and the radii with L sets in. This variation is due to the fact that the wavelength λ^*(T) of the ordering (defined from the wavenumber q^* where S(q) is maximal at λ^* = 2 π/q^*) in general is incommensurable with the box. The competition of two nontrivial lengths ξ(T), λ^* (T) with L makes the straigthforward application of finite size scaling techniques impossible, unlike the case of polymer blends. Since also the specific heat is found to have a broad rounded peak near the transition only, locating the transition accurately from Monte Carlo simulations remains an unsolved problem.     

FT-IR Investigation of Rare-Earth and Metal-Ion Solvation. Part 14. Interaction between uranyl perchlorate and dimethyl sulfoxide in anhydrous acetonitrile

The interaction between the uranyl ion and perchlorate in anhydrous acetonitrile has been investigated by FT-IR and Raman spectroscopy. Vibrations assigned to uncoordinated (u), monodentate (m), and bidentate (b) perchlorate anions were identified in 0.075M solutions. Quantitative data indicate that perchlorate is distributed as follows: 37 ± 2% are uncoordinated, 36 ± 7% are monodentate, and 27 ± 7% are bidentate. This is in agreement with the conductivity of the solutions which is at the lower end of the range accepted for 1:1 electrolytes. The splittings v₄–v₁(m) and v₈–v₁(b) of 147 and 246 cm^?1, respectively, point to a large inner-sphere interaction. An equilibrium occurs between two differently coordinated species. Various amounts of DMSO were added to 0.05M perchlorate solutions (R′ = [DMSO]_t/[UO]_t = 1–10). The v₇ (SO) and v₂₂ (CS) vibrations of DMSO were used to determine the average number of coordinated DMSO molecules per uranyl ion, which is close to 4. Some bidentate perchlorate ions are still present in these solutions, but all the MeCN molecules (2.6 on average) are expelled out of the inner coordination sphere. The data can again be interpreted in terms of an equilibrium between differently coordinated species. The average coordination number of the uranyl ion is 4.4, as the perchlorate salt in MeCN solution, and may be somewhat smaller in the presence of DMSO. The possible presence of dimeric species is also discussed.     

Kristallstruktur,Schwingungsspektren und Normalkoordinatenanalyse von (n‐Bu4N)2[{Ru(NO)ClI2}2(μ‐I2)] · 2 I2

Crystal Structure, Vibrational Spectra, and Normal Coordinate Analysis of ( n ‐Bu₄N)₂[{Ru(NO)ClI₂}₂(μ‐I₂)] · 2 I₂ By treatment of (n‐Bu₄N)₂[Ru(NO)I₅] with (n‐Bu₄N)Cl in dichloromethane (n‐Bu₄N)₂[{Ru(NO)ClI₂}₂(μ‐I₂)] is formed. The X‐Ray structure determination on a single crystal of (n‐Bu₄N)₂[{Ru(NO)ClI₂}₂(μ‐I₂)] · 2 I₂ (monoclinic, space group I 2/a, a = 20.446(6), b = 11.482(8), c = 27.225(3) Å, β = 107.51(4)°, Z = 4) reveals a dinuclear iodine bridged structure, in which the chlorine atoms are trans positioned to the nitrosyl groups. The low temperature IR and Raman spectra have been recorded of (n‐Bu₄N)₂[{Ru(NO)ClI₂}₂(μ‐I₂)] · 2 I₂ and are assigned by normal coordinate analysis. A good agreement between observed and calculated frequencies is achieved. The valence force constants are f_d(NO) = 14.08, f_d(RuN) = 5.58, f_d(RuCl) = 1.52, f_d(RuI_t) = 0.90 and f_d(RuI_b) = 0.76 mdyn/Å.     

A laser flash photolysis/IR diode laser absorption study of the reaction of chlorine atoms with selected alkanes

A high‐resolution IR diode laser in conjunction with a Herriot multiple reflection flow‐cell has been used to directly determine the rate coefficients for simple alkanes with Cl atoms at room temperature (298 K). The following results were obtained: k(Cl + n‐butane) = (1.91 ± 0.10) × 10^?10 cm³ molecule^?1 s^?1, k(Cl + n‐pentane) = (2.46 ± 0.12) × 10^?10 cm³ molecule^?1 s^?1, k(Cl + iso‐pentane) = (1.94 ± 0.10) × 10^?10 cm³ molecule^?1 s^?1, k(Cl + neopentane) = (1.01 ± 0.05) × 10^?10 cm³ molecule^?1 s^?1, k(Cl + n‐hexane) = (3.44 ± 0.17) × 10^?10 cm³ molecule^?1 s^?1 where the error limits are ±1σ. These values have been used in conjunction with our own previous measurements on Cl + ethane and literature values on Cl + propane and Cl + iso‐butane to generate a structure activity relationship (SAR) for Cl atom abstraction reactions based on direct measurements. The resulting best fit parameters are k_p = (2.61 ± 0.12) × 10^?11 cm³ molecule^?1 s^?1, k_s = (8.40 ± 0.60) × 10^?11 cm³ molecule^?1 s^?1, k_t = (5.90 ± 0.30) × 10^?11 cm³ molecule^?1 s^?1, with f( ? CH₂^? ) = f (? CH₂^? ) = f (?C?) = f = 0.85 ± 0.06. Tests were carried out to investigate the potential interference from production of excited state HCl(v = 1) in the Cl + alkane reactions. There is some evidence for HCl(v = 1) production in the reaction of Cl with shape n‐hexane. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 86–94, 2002     

Promoting Difficult Carbon–Carbon Couplings: Which Ligand Does Best?

A Pd complex, cis‐[Pd(C₆F₅)₂(THF)₂] ( 1 ), is proposed as a useful touchstone for direct and simple experimental measurement of the relative ability of ancillary ligands to induce C?C coupling. Interestingly, 1 is also a good alternative to other precatalysts used to produce Pd⁰L. Complex 1 ranks the coupling ability of some popular ligands in the order P^tBu₃>o‐TolPEWO‐F≈tBuXPhos>P(C₆F₅)₃≈PhPEWO‐F>P(o‐Tol)₃≈THF≈tBuBrettPhos?Xantphos≈PhPEWO‐H?PPh₃ according to their initial coupling rates, whereas their efficiency, depending on competitive hydrolysis, is ranked tBuXPhos≈P^tBu₃≈o‐TolPEWO‐F>PhPEWO‐F>P(C₆F₅)₃?tBuBrettPhos>THF≈P(o‐Tol)₃>Xantphos>PhPEWO‐H?PPh₃. This “meter” also detects some other possible virtues or complications of ligands such as tBuXPhos or tBuBrettPhos.     

Novel Method of Producing Polymer Gels in Aqueous Solution Using UV Irradiation

Summary: We developed a novel method of producing polymer gels in aqueous solution using UV irradiation. Persulfates were effective photosensitive initiators of polymerization and/or gelation of acryloyl‐type monomers/polymers. The gelation was confirmed by an abrupt increase in light scattering intensity, 〈I(q)〉_T, at the gelation point. The gelation method entails significant advantages: it does not need any cross‐linkers, temperature control (heating), and additives except the persulfate.

The UV irradiation time dependence of light scattering intensity, 〈I(q)〉_T, for pre‐gel solutions containing N‐isopropylacrylamide (NIPAm) and/or ammonium persulfate (APS).