Swelling behavior of emulsion polymer particles: comparison between fully cross-linked and partially cross-linked poly(acrylate) latexes

Summary Measurement of swelling is used to estimate the extent of cross-linking of latex particles prepared by emulsion polymerization. In this paper we report swelling data as a function of solvent activity for two latexes: (1) a poly(butylacrylate) (PBA) latex, and (2) a poly(isodecylacrylate) latex. In the latter case comparison is made between the swelling behavior of fully cross-linked, i.e., networks without free polymer chains, and partially cross-linked latexes. It is demonstrated that the equilibrium swelling properties are only slightly affected by the presence of uncross-linked chains. Swelling gives reliable results for the cross-link density only if the latex does not contain free chains. Received: 3 March 1998/Revised version: 13 May 1998/Accepted: 10 June 1998     

Specific volume of polystyrene networks

We have described a method for the measurement of the specific volume of polymer networks at different degrees of swelling. We have observed a very small difference between the apparent specific volume of polystyrene in the swollen gel state and in solution in the same solvent and at the same polymer concentration. This indicates a small variation in the chain expansion with the degree of swelling. Moreover, our precise measurements of the swelling parameters confirm the interdispersion phenomenon as the main process for the swelling in a ‘theta’ solvent.     

Evaluation by various experimental approaches of the crosslink density of urethane networks based on hydroxyl‐terminated polybutadiene

Crosslink density (CLD) is an important characteristic for elastomeric polymer networks. The mechanical and viscoelastic properties of the elastomers are critically dependant on the CLD. Several methods have been adopted for its determination, but swelling and stress–strain methods continue to be more popular because of the convenience associated with these techniques. In this article, the determination of CLD of allophanate–urethane networks based on hydroxyl‐terminated polybutadiene and toluene diisocyanate with swelling and stress–strain methods is reported. The Flory–Rhener relationship was applied to calculate CLD from the swelling data. CLDs were also calculated from the initial slope of the stress–strain curve (Young's modulus), Mooney–Rivlin plots, equilibrium relaxation moduli, and dynamic mechanical properties. A comparison was drawn among the values obtained with the various methods. Although the CLD values obtained from Mooney–Rivlin plots were slightly lower than those obtained from swelling data, the values obtained with Young's modulus and storage modulus were considerably higher. The values obtained with swelling and equilibrium relaxation moduli data were very close to each other. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3129–3133, 2007     

Latex interpenetrating polymer networks based on acrylic polymers. IV. The influence on mechanical properties of the time of swelling the seed particles with the second monomer

Two latex interpenetrating polymer networks, one based on a partially compatible pair and the other based on an incompatible pair of polymers, were prepared by a two-stage emulsion polymerization. To investigate the effect of swelling the first formed polymer particles with the second monomer, the second stage of the synthesis was conducted after allowing the second monomer to be in contact with the seed latex for specified periods of time. Fabricated samples of these interpenetrating polymer networks were subjected to hardness, stress–strain, and dynamic mechanical measurements. The results showed an enhancement in mixing of the two networks in the case of the partially compatible pair and a detectable increase in the level of mixing for the incompatible pair.     

Monte Carlo simulation of two interpenetrating polymer networks: Structure, swelling, and mechanical properties

The swelling and mechanical properties of various interpenetrating polymer networks (IPNs) were studied. Six networks made from permutations of a moderately crosslinked polyelectrolyte network (ref), a moderately crosslinked neutral polymer network (net1), and a highly crosslinked polyelectrolyte network (net2) were first swollen in water and structural properties such as end-to-end chain lengths and radial distribution functions were compared with the component networks' equilibrium properties. The swelling of composite IPNs was discussed in terms of a balance between the osmotic pressure due to mobile counterions and the restoring force of the network chains, which act in parallel to counteract the osmotic swelling. For the ref-net2 system, the strong stretching of net2 chains increases the network restoring force and the further swelling due to the counterions is suppressed. The swollen networks were then uniaxially stretched, and equilibrium stress-strain plots were obtained up to high extension ratios. The equilibrium volume decreased upon uniaxial extension, and the elastic moduli of IPNs of the A-A type were slightly greater than that of their respective single networks.     

Synthesis and properties of solvent absorptive methyl methacrylate‐divinylbenzene copolymer beads

Methyl methacrylate‐divinylbenzene copolymer beads were synthesized by radical suspension polymerization. The effects of the divinylbenzene concentration and the composition of the toluene/heptane diluent were studied with regard to the polymer bead formation, surface morphology, solvent swelling ratio, and absorption kinetics. The crosslinking density and diluent composition were responsible for solvent swelling. The interaction between the polymer and the diluents is attributed to phase separation, which controls the formation of a network‐type or pore‐type polymer, or a combination. For the optimum bead swelling in toluene, a combined morphology of more flexible polymer networks and a small amount of pores is essential for the desired absorption–desorption behavior. Dynamic swelling behavior of the polymer beads was elucidated. The mechanism of toluene transport into the beads became more a relaxation control. POLYM. ENG. SCI., 47:447–459, 2007. © 2007 Society of Plastics Engineers.     

Swelling and collapse of polymer networks

The swelling of a polymer network in a good solvent and of the collapse of this sample in a poor solvent is discussed theoretically for networks prepared in the presence of a large amount of diluent. The notation used is convenient for comparison with the theory of the swelling and collapse of a single macromolecule. The reference state for the networks under consideration must be chosen near the θ temperature for the corresponding linear macromolecule. For a free network and a network with fixed dimensions along one or two axes we obtain asymptotic results for the swelling of the network in a good solvent; these do not coincide with the classical Flory results. Results for the collapse of the network, which takes place upon cooling below the θ-point are also obtained. The collapse can occur either as a discrete first order phase transition (if the network chains are stiff or if it is stretched along one or two axes), or as a continuous non-phase transition (located in a narrow temperature range).     

Case II swelling of poly(ethylene terephthalate) in organic solvents

The swelling kinetics of crystalline PET films in chloroform–n-hexane mixtures were examined as a function of chloroform concentration. With increasing concentration, the swelling mechanism varied from Fickian to Case II behavior. The dependence of the swelling mechanism on the equilibrium uptake and activation energy for swelling were thoroughly compatible with those presented by other workers. From a viewpoint of superposition of Fickian and Case II swelling, the intermediate swelling between the above two limiting cases was analyzed by Kwei's equation. The magnitude of the diffusion coefficient obtained was remarkably smaller than that presented for the swollen amorphous polymer. The magnitude of the penetration velocity is also discussed in comparison with the data for amorphous polymer.     

Trisodium trimetaphosphate crosslinked xanthan networks: synthesis,swelling, loading and releasing behaviour

Xanthan (Xan) is a biocompatible and biodegradable polysaccharide with a promising potential as substrate for controlled drug delivery applications. Xan based hydrogels were synthesized in alkaline medium using trisodium trimetaphosphate (STMP) as crosslinking agent. Hydrogels with various crosslinking agent/polymer ratios were synthesized and subsequently characterized by the means of elemental analysis and dynamic swelling degree, model compound loading and releasing behaviour. Two physical parameters (crosslinking density and phosphate charge) are manifesting antagonistic actions by stiffening or disrupting the three-dimensional macromolecular ensemble. The highest swelling degree was obtained using an intermediate STMP:Xan ratio in which case the opposing effects of the two forces are well balanced. The synthesized networks are pH sensitive. In acid and alkaline media the swelling degrees are lower by comparison to neutral pH. The entrapping and releasing behaviour of the newly synthesized xanthan networks were studied using methylene blue as a cationic model molecule. The releasing kinetics present a first-order model.     

Three different types of quasi-model networks: synthesis by group transfer polymerization and characterization

Summary Group transfer polymerization (GTP) chemistry was employed for the preparation of polymethacrylate networks of controlled structure (quasi-model networks) of three different types: (a) regular quasi-model networks, in which all polymer chains were linked at their ends, leaving, in principle, no free chain ends, (b) crosslinked star polymer quasi-model networks, in which star polymers were interlinked via half of their chains, letting the other half free (dangling), and (c) shell-crosslinked polymer quasi-model networks, in which the outer part of the network contained polymer arms (dangling chains). Combination of hydrophilic and hydrophobic monomers led to amphiphilic networks whose aqueous swelling behavior was characterized gravimetrically.     

Transport models for swelling and dissolution of thin polymer films

Fundamental models have been developed to describe swelling and dissolution of glassy polymer thin films. The models account for solvent penetration by either Fickian or Case II diffusion mechanims. The convective flux due to local swelling as the solvent penetrates is included. Chain disentanglement at the polymer-developer solution interface is scaled with the local solvent concentration and polymer molecular weight using reptation theory. The effective surface concentration during dissolution is estimated by applying thermodynamics of swollen networks to the entangled polymer. Swelling and dissolution of thin polymer films have direct application to microlithography. Various molecular and processing parameters affect the outcome of resist development. The utility of the models for selecting appropriate developer solvents, minimizing resist swelling, and providing a better understanding of the swelling and dissolution of resists is demonstrated.     

Synthesis and swelling characteristics of pH and thermoresponsive interpenetrating polymer network hydrogel composed of poly(vinyl alcohol) and poly(acrylic acid)

The swelling behavior of novel pH- and temperature-sensitive interpenetrating polymer networks (IPNs) composed of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAAc) in water was investigated. The PVA/PAAc IPN hydrogels were synthesized by UV irradiation, followed by a repetitive freezing and thawing process by which PVA hydrogel networks were formed inside of cross-linked PAAc chains. The swelling behaviors of these IPNs were analyzed in buffer solution at various pH and temperature ranges. Swelling ratios of all IPNs were relatively high, and they showed reasonable sensitivity to both pH and temperature. Hydrogels showed both the positive and negative swelling behaviors depending on PAAc content. IPN46 showed the positive temperature-sensitive swelling behaviors and its stepwise changes in swelling ratio was about 1.8 and 2.0 obtained between 25 and 45°C at pH 7, and between pH 4 and 7 at 35°C, respectively. The positive temperature dependence is attributed to the formation and dissociation of hydrogen bonding complexes between PVA and PAAc. These IPNs are expected to show a pH- and temperature-sensitive drug release according to the stepwise behavior at this temperature region. © 1996 John Wiley & Sons, Inc.     

Characterization of the network structure of hydroxyl terminated poly(butadiene) elastomers prepared by different reactive systems

Three types of hydroxyl terminated poly(butadiene) (HTPB) networks having different NCO/OH reactive group ratios were prepared using three different reactive systems (i.e., Desmodur N-100 pluriisocyanate, isophorone diisocyanate (IPDI)/trimethylol propane (TMP), and hexamethylene diisocyanate (HMDI)/TMP). Desmodur N-100 and TMP were used as polyfunctional reactants. The polymer–solvent interaction parameters (χ₁) for HTPB–tetrahydrofuran (THF) and HTPB–chloroform systems at 45°C were determined, using a vapor pressure osmometer (VPO), as 0.31 and 0.24, respectively. Equilibrium swelling values of the networks in THF and chloroform and the data obtained by osmometry were further used for the calculation of the mean number-average molecular weight between junction points (M _c) of HTPB networks through the Flory-Rehner equation. The M _c values of each network, which were calculated from the swelling data obtained in THF and chloroform using the corresponding χ₁ parameters for polymer–solvent systems, were found to be nearly the same. The changes in the mechanical, swelling, and the solubility properties of the networks prepared by three different reactive systems were followed. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 1129–1135, 1998     

Polyurethane-poly(methyl methacrylate) interpenetrating polymer networks: 2. Influence of compositional parameters on the synthesis; physical properties

According to a previously established general preparation scheme, polyurethane-poly(methyl methacrylate) interpenetrating polymer networks with various compositions and crosslinker contents were prepared. The influence of kinetics of the individual networks on the resulting composites was also examined. Only about 5% soluble species were extractible, thus showing a satisfactory completion of the different reaction systems. Physical properties such as transparency, refractive index, density and swelling behaviour were determined.     

SBS／聚（苯乙烯—甲基丙烯酸盐）热塑性IPN的相区尺寸研究

从聚合物混合的热力基础出发，推导出ＳＢＳ／聚（苯乙烯－甲基丙烯酸盐）热塑性ＩＰＮ的相区尺寸与其组成的理论关系式。同时，使用小角Ｘ－光散射技术对相区尺寸进行测量，实验结果与上述理论关系计算结果基本一致。     

Chiral recognition of enantiomeric isobornyl methacrylate‐containing hydrogels with α‐cyclodextrin

Two enantiomers of isobornyl methacrylate (iBMA) were prepared by reducing (1R,4R)‐(+)‐camphor and (1S,4S)‐(?)‐camphor followed by simple methacrylation reaction. The iBMA enantiomers were incorporated into hydrophilic polymer networks by free radical polymerization with N,N‐dimethylacrylamide and diethylene glycol dimethacrylate at different molar ratios. The influence of α‐cyclodextrin (α‐CD) and randomly methylated β‐cyclodextrin (rβ‐CD), and thereby enantioselectivity, on the swelling behaviour of the enantiomeric networks in water and alcoholic solutions was examined. An increase of swelling was observed on addition of α‐CD and rβ‐CD. While rβ‐CD showed a greater influence on the swelling itself, only α‐CD was able to achieve a minor differentiation between the polymer networks by their enantiomeric components and therefore a chiral recognition of the iBMA moieties. These results were validated using rheological measurements. © 2015 Society of Chemical Industry     

Synthesis and swelling properties of pH‐ and temperature‐sensitive interpenetrating polymer networks composed of polyacrylamide and poly(γ‐glutamic acid)

Novel hydrogels of interpenetrating polymer networks (IPNs) composed of polyacrylamide and poly(γ‐glutamic acid) were synthesized. In these systems, both polymers were crosslinked independently; this reduced the potential loss of a polymer during the washing process, as often occurs in semi‐IPN systems. Interpolymer interactions were investigated with Fourier transform infrared spectroscopy and differential scanning calorimetry. These studies suggested possible interactions between both polymers by the formation of hydrogen bonds. The swelling behavior of these hydrogels was analyzed by immersion of the hydrogel samples in deionized water at 25 and 37°C and in buffer solutions with pHs of 3, 7, and 10. The kinetics of swelling showed increases in the values of the swelling ratio with increasing immersion time in the swelling medium, molar proportion of the biopolymer in the hydrogel, temperature, and pH of the swelling medium. All of the hydrogels swelled rapidly and reached equilibrium in an average time of 40 min. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Confinement effects on the kinetics of formation of sequential semi-interpenetrating polymer networks

Summary Peculiarities of formation kinetics of sequential semi-interpenetrating polymer networks based on crosslinked polyurethane with different cross-linking density and linear polystyrene and polybutylmethacrylate have been studied. Polyurethane networks were synthesized differing in molecular mass M_c of the chains between cross-links. Monomeric styrene and butyl methacrylate were introduced into these networks by swelling them in monomers up to equilibrium. The kinetics of polymerization of monomers in swollen networks was investigated. The experimental data show the dependence of the kinetic parameters of polymerization on M_c, this dependence being different for various monomers. Sharp discrepancy in molecular mass distribution of polymers formed in various matrices has been observed. The differences in dependencies of reaction kinetics and molecular mass distribution are supposed to be connected to various dependence of the chain growth and termination of various monomers on the density of network, i.e. on the confinements imposed by the intranetwork space.     

Castor oil based UV-curable polyurethane-acrylate interpenetrating networks

Castor oil was reacted in varying ratios with β-isocyanatoethyl methacrylate to form a liquid urethane–methacrylate prepolymer. This prepolymer was then cured using ultraviolet radiation to form a series of base polymer networks or using various methacrylates to form conetworks. By swelling the base networks with the appropriate methacrylate monomers, semi- and full interpenetrating networks (IPNs) were prepared with similar compositions. All of the materials formed transparent films. Results of swelling experiments, dynamic mechanical analysis, differential scanning calorimetry, and small angle x-ray scattering are discussed.