Surface-modulated skin layers of thermal responsive hydrogels as on-off switches: I. Drug release.

Thermosensitive co-polymers of isopropyl acrylamide (IPAAm) with butyl methacrylate (BMA) are capable of 'on-off' regulation of drug release in response to external temperature changes due to skin formation with increasing temperature. To clarify the role of the surface-modulated skin and controlled pulsatile drug release patterns, the surface shrinking process was regulated by changing the length of the methacrylate alkyl side-chain. Release of indomethacin in response to stepwise temperature changes between 20 and 30 degrees C from co-polymers of IPAAm with BMA, hexyl methacrylate (HMA), and lauryl methacrylate (LMA) was studied. The drug release rate during the 'on' state (20 degrees C) remained constant before and after the 'off' state (30 degrees C) when the period of the 'off' state was increased. These results suggest that the drug in the polymeric matrices diffused from the inside to the surface during the 'off' state even when no drug release was seen. The length of alkyl side-chain was found to be an important parameter in controlling the thickness and density of the surface skin layer.     

Surface-modulated skin layers of thermal responsive hydrogels as on-off switches: I. Drug release

Thermosensitive co-polymers of isopropyl acrylamide (IPAAm) with butyl methacrylate (BMA) are capable of 'on-off' regulation of drug release in response to external temperature changes due to skin formation with increasing temperature. To clarify the role of the surface-modulated skin and controlled pulsatile drug release patterns, the surface shrinking process was regulated by changing the length of the methacrylate alkyl side-chain. Release of indomethacin in response to stepwise temperature changes between 20 and 30°C from co-polymers of IPAAm with BMA, hexyl methacrylate (HMA), and lauryl methacrylate (LMA) was studied. The drug release rate during the 'on' state (20°C) remained constant before and after the 'off' state (30°C) when the period of the 'off' state was increased. These results suggest that the drug in the polymeric matrices diffused from the inside to the surface during the 'off' state even when no drug release was seen. The length of alkyl side-chain was found to be an important parameter in controlling the thickness and density of the surface skin layer.     

Modulating the phase transition temperature and thermosensitivity in N-isopropylacrylamide copolymer gels

—Temperature-responsive copolymer (or ternary copolymer) gels of N-isopropylacrylamide (IPAAm) were synthesized with hydrophobic alkyl methacrylate (RMA), hydrophilic acrylamide (AAm), N,N'-dimethylacrylamide (DMAAm), and N-acryloylpyrrolidine (APy) as comonomers. The effects of these comonomers on the phase transition temperature (LCST) and the thermosensitivity have been discussed. The LCST of poly(IPAAm) gel in phosphate buffered saline (PBS) was lowered by the introduction of hydrophobic RMA, and the change in equilibrium swelling ratio with temperature change became smaller with an increase in RMA content. However, a stable skin layer to achieve complete 'on-off' regulation of drug release was formed at a higher temperature by RMA due to hydrophobic interaction of alkyl chains. The LCST of poly(IPAAm-co-AAm) gel increased with an increase in AAm content. However, the thermosensitivity of the gel became smaller. It was suggested that hydrophilic AAm prevented the formation of a dense skin layer at a higher temperature. It was difficult to obtain a complete 'off' state due to an insufficiently dense skin layer in order to stop the drug release. The LCST was raised and great thermosensitivity was possible by the introduction of DMAAm or APy. Poly(IPAAm-co-DMAAm) enabled 'on-off' drug release in response to smaller temperature changes around the body temperature. The molecular design to control transition temperature and thermosensitivity of gel was established.     

Effect of methylene chain length in phospholipid moiety on blood compatibility of phospholipid polymers

To investigate the effects of the methylene chain length between the phospholipid polar group and the backbone on blood compatibility of a phospholipid polymer, copolymers of ω-methacryloyloxyalkyl phosphorylcholine (MAPC) with n-butyl methacrylate (BMA) were synthesized. The methylene chains were ethylene (n = 2), tetramethylene (n = 4), and hexamethylene (n = 6). Every MAPC copolymer with an MAPC mole fraction in the range of 0.1-0.3 was soluble in ethanol but only swelled in water, and the equilibrium water fraction of the water-swollen MAPC copolymer membrane decreased with the length of the methylene chain. When a rabbit platelet-rich plasma was applied on the MAPC copolymer surface with an 0.1 MAPC mol fraction for 180 min, the number of adhered platelets depended on the length of the methylene chain in the MAPC moiety of the copolymer. The amount of phospholipid adsorbed on the MAPC copolymer from human plasma was larger than that on hydrophobic poly(BMA) and increased with the length of the methylene chain in the MAPC moiety. That is, the reduction of platelet adhesion corresponded to the increase in the amount of phospholipid adsorbed on the MAPC copolymer.     

The effect of substrate molecular mobility on surface induced immune complement activation and blood plasma coagulation

Changing the length of the alkyl ester side chain in poly(alkyl methacrylates) provides a unique opportunity to systematically vary the mobility of the polymer chains, or in other words vary the glass transition temperature (T(g)), without greatly affect the solid surface energy (gamma(s)) of the polymer. A series of poly(alkyl methacrylate) coatings was therefore analysed with regard to the human immune complement (IC) activation and the surface associated blood plasma coagulation cascade (CC) properties. For the IC and CC measurements we used a quartz crystal microbalance (QCM) where we modified the chemistry of the sensor surface by applying 10-30 nm thick poly(alkyl methacrylate) coatings. The surface energy was calculated from water contact angles and small differences between the coatings were observed. The surface chemistry of the coatings, as determined with X-ray photoelectron spectroscopy (XPS), showed no deviation from expected compositions. Tapping mode atomic force microscopy (TM-AFM) measurements revealed that all coatings displayed similar morphology and the roughness was in the range of 0.7-0.9 nm. Increased polymer mobility correlated with a decrease in IC activation, measured as a decreased C3c deposition at the surface. The surface induced CC, measured as fibrin clot formation at the surface, was different between the different coatings but no correlation with molecular mobility was observed. Thus, the molecular mobility of the polymer chains had a major effect on both the IC and the CC and it seems that different aspects of the chemistry of the solid surface regulate activation of the IC and the CC.     

Multifunctional triblock copolymers for intracellular messenger RNA delivery

Messenger RNA (mRNA) is a promising alternative to plasmid DNA (pDNA) for gene vaccination applications, but safe and effective delivery systems are rare. Reversible addition-fragmentation chain transfer (RAFT) polymerization was employed to synthesize a series of triblock copolymers designed to enhance the intracellular delivery of mRNA. These materials are composed of a cationic dimethylaminoethyl methacrylate (DMAEMA) segment to mediate mRNA condensation, a hydrophilic poly(ethylene glycol) methyl ether methacrylate (PEGMA) segment to enhance stability and biocompatibility, and a pH-responsive endosomolytic copolymer of diethylaminoethyl methacrylate (DEAEMA) and butyl methacrylate (BMA) designed to facilitate cytosolic entry. The blocking order and PEGMA segment length were systematically varied to investigate the effect of different polymer architectures on mRNA delivery efficacy. These polymers were monodisperse, exhibited pH-dependent hemolytic activity, and condensed mRNA into 86-216?nm particles. mRNA polyplexes formed from polymers with the PEGMA segment in the center of the polymer chain displayed the greatest stability to heparin displacement and were associated with the highest transfection efficiencies in two immune cell lines, RAW 264.7 macrophages (77%) and DC2.4 dendritic cells (50%). Transfected DC2.4 cells were shown to be capable of subsequently activating antigen-specific T cells, demonstrating the potential of these multifunctional triblock copolymers for mRNA-based vaccination strategies.     

Novel bifunctional polymer with reactivity and temperature sensitivity

To introduce reactive groups into temperature-responsive polymeric chains of poly(N-isopropylacrylamide) (PIPAAm), IPAAm is copolymerized with other monomer such as acrylic acid (AAc). IPAAm homopolymer exhibited temperature-responsive properties and phase transition at 32 degrees C, however, the lower critical solution temperature (LCST) of the IPAAm-AAc copolymer shifts to a higher temperature and the phase transition becomes insensitive with increasing AAc content. To achieve a useful bifunctional copolymer containing both reactivity and temperature-sensitivity, we assumed that the homopolymer-like structure in the polymer chain would be required to maintain a sensitive temperature response with functional groups. Therefore, we designed a reactive monomer, 2-carboxyisopropylacrylamide (CIPAAm), and investigated its copolymerization with IPAAm. The important characteristic of the poly(IPAAm-co-CIPAAm) structure is that it was composed of the same polymer backbone and isopropylamide groups and some additional carboxyl groups. The transmittance measurement of the polymer aqueous solution revealed that phase transition of IPAAm-co-CIPAAm random copolymer occurred within a very narrow temperature range in pH 6.4, 7.4, and also even 9.0 phosphate buffered solution. These profiles were almost same as that of IPAAm homopolymer. While, under the same conditions, phase transition properties of poly(IPAAm-co-AAc)s solution were considerably influenced by small AAc content. We succeeded with the preparation of bifunctional polymer that possessed reactive functional groups and very sensitive response to temperature change.     

Biodegradable poly(D,L-lactic acid)-poly(ethylene glycol)-monomethyl ether diblock copolymers: structures and surface properties relevant to their use as biomaterials

To obtain biodegradable polymers with variable surface properties for tissue culture applications, poly(ethylene glycol) blocks were attached to poly(lactic acid) blocks in a variety of combinations. The resulting poly(D,L-lactic acid)-poly(ethylene glycol)-monomethyl ether (Me.PEG-PLA) diblock copolymers were subject to comprehensive investigations concerning their bulk microstructure and surface properties to evaluate their suitability for drug delivery applications as well as for the manufacture of scaffolds in tissue engineering. Results obtained from 1H-NMR, gel permeation chromatography, wide angle X-ray diffraction and modulated differential scanning calorimetry revealed that the polymer bulk microstructure contains poly(ethylene glycol)-monomethyl ether (Me.PEG) domains segregated from poly(D,L-lactic acid) (PLA) domains varying with the composition of the diblock copolymers. Analysis of the surface of polymer films with atomic force microscopy and X-ray photoelectron spectroscopy indicated that there is a variable amount of Me.PEG chains present on the polymer surface, depending on the polymer composition. It could be shown that the presence of Me.PEG chains in the polymer surface had a suppressive effect on the adsorption of two model peptides (salmon calcitonin and human atrial natriuretic peptide). The possibility to modify polymer bulk microstructure as well as surface properties by variation of the copolymer composition is a prerequisite for their efficient use in the fields of drug delivery and tissue engineering.     

Novel bifunctional polymer with reactivity and temperature sensitivity

To introduce reactive groups into temperature-responsive polymeric chains of poly(N-isopropylacrylamide) (PIPAAm), IPAAm is copolymerized with other monomer such as acrylic acid (AAc). IPAAm homopolymer exhibited temperature-responsive properties and phase transition at 32°C, however, the lower critical solution temperature (LCST) of the IPAAm-AAc copolymer shifts to a higher temperature and the phase transition becomes insensitive with increasing AAc content. To achieve a useful bifunctional copolymer containing both reactivity and temperature-sensitivity, we assumed that the homopolymer-like structure in the polymer chain would be required to maintain a sensitive temperature response with functional groups. Therefore, we designed a reactive monomer, 2-carboxyisopropylacrylamide (CIPAAm), and investigated its copolymerization with IPAAm. The important characteristic of the poly(IPAAm-co-CIPAAm) structure is that it was composed of the same polymer backbone and isopropylamide groups and some additional carboxyl groups. The transmittance measurement of the polymer aqueous solution revealed that phase transition of IPAAm-co-CIPAAm random copolymer occurred within a very narrow temperature range in pH 6.4, 7.4, and also even 9.0 phosphate buffered solution. These profiles were almost same as that of IPAAm homopolymer. While, under the same conditions, phase transition properties of poly(IPAAm-co-AAc)s solution were considerably influenced by small AAc content. We succeeded with the preparation of bifunctional polymer that possessed reactive functional groups and very sensitive response to temperature change.     

Competitive adsorption between phospholipid and plasma protein on a phospholipid polymer surface.

The competitive adsorption of proteins and phospholipids on omega-methacryloyloxyalkyl phosphorylcholine (MAPC) polymer was evaluated in this study. Albumin, fibrinogen, and dimyrstoyl phosphatidylcholine (DMPC) were used as model components. The amount of DMPC adsorbed on the MAPC polymers increased with an increase in the MAPC unit composition of the polymer. The methylene chain length of the MAPC unit was another factor influencing the DMPC adsorption when the MAPC unit composition of the MAPC polymer was low. The state of albumin and DMPC liposome adsorbed on the 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer was determined by dynamic contact angle (DCA) measurement. The adsorption strength of albumin on the MPC polymer was weaker than that on the poly[n-butyl methacrylate (BMA)], that is, the albumin was detached from the MPC polymer during the rinsing process. On the poly(BMA) surface, no difference in the shape of the DCA loops before and after contact with the DMPC liposomal suspension was observed. Fibrinogen adsorption on the MAPC polymer was detected by gold-colloid labeled immunoassay. The amount of fibrinogen adsorbed on every MAPC polymer surface was reduced by addition of the DMPC liposome in the fibrinogen solution. The number of platelets adhered on the MAPC polymer was also decreased when the DMPC liposome was present in the fibrinogen solution during pretreatment. We concluded that phospholipids were preferentially adsorbed on the MAPC polymer surface compared with plasma protein and that the adsorbed phospholipids played an important role in showing an excellent blood compatibility on the MAPC polymer.     

Effect of reduced protein adsorption on platelet adhesion at the phospholipid polymer surfaces

We prepared polymers having a phospholipid polar group, poly[ω-methacryloyloxyalkyl phosphorylcholine (MAPC)-co-n-butyl methacrylate(BMA)], as new biomedical materials and evaluated their blood compatibility with attention to protein adsorption and platelet adhesion. The total amount of proteins adsorbed on the polymer surface from human plasma was determined, and the distribution of adsorbed proteins on the plasma-contacting surface was analyzed. The amount of proteins adsorbed on every poly(MAPC-co-BMA) was small compared with that observed on polymers without the phospholipid polar group. However, there was no significant difference in the amount of adsorbed proteins on the poly(MAPC-co-BMA) even when the methylene chain length between the phospholipid polar group and the backbone in the MAPC moiety was altered. Platelet adhesion on the polymer surface from a platelet suspension in a buffered solution was evaluated with and without plasma treatment on the surface. When a rabbit platelet suspension was brought into contact with the poly(BMA) surface after treatment with plasma, many platelets adhered and aggregated. However, a reduced amount of platelet adhered on the poly(BMA) was found in the case of direct contact with the platelet suspension. On the other hand, the poly(MAPC-co-BMA)s could inhibit platelet adhesion under both conditions. Based on these results, it can be concluded that the proteins adsorbed on the surface play an important role in determining the platelet adhesion and suppression of the protein adsorption on the surface, which is one of the most significant ways of inhibiting platelet adhesion.     

Influential factors on temperature-controlled gene expression using thermoresponsive polymeric gene carriers

Thermoresponsive random copolymers, poly[N-isopropylacrylamide (IPAAm)-co-2-(dimethylamino)ethyl methacrylate (DMAEMA)-co-butylmethacrylate (BMA)], were synthesized in three compositions, and their in vitro gene transfection efficiency to cultured cells at different incubation conditions was measured using β-galactosidase as a marker gene. These three copolymers increased gene expression when the cell incubation temperature was lowered below 37°C. This increase in transfection efficiency when temperature was lowered is considered to be due to enhanced DNA release from the polymer-DNA complex in cells. The influence of complex preparation conditions (charge ratio and temperature) and cell incubation conditions (incubation period with the complex, cooling temperature, timing, and period) was analyzed to elucidate the mechanism of this gene expression control as well as to maximize the increase in gene expression on lowering of the cell incubation temperature. One copolymer showed a nine-fold increase in gene expression on lowering of the temperature to 20°C for 3 h. In analyses of temperature effects in the complex formation procedure on the gene expression, tight complex formation was considered to contribute to efficient cell uptake and/or evasion from enzymatic DNA degradation.     

Blood cell separation using amphiphilic copolymers containing N,N-dimethylacrylamide

To develop leukocyte removal filters effective for whole blood, amphiphilic copolymers based on N,N-dimethylacrylamide were synthesized and evaluated as coating materials for poly(ethylene terephthalate) filters. The copolymers with methyl methacrylate or 2-hydroxypropyl methacrylate as a comonomer showed higher platelet permeation ratios (more than 90%) than that of the copolymer with n-butyl methacrylate, though the logarithmic reductions of leukocytes by these copolymers were less than four. An increase in the platelet permeation for whole blood tended to increase the leukocyte permeation. The permeation of both platelets and leukocytes increased with the amount of copolymer coated on the filters because of the change in the physical properties such as the average pore size, total surface area, and total pore volume of coated filters. These results confirm that both the chemical and physical properties of the filters play important roles to control the permeation behavior.     

Low-temperature structural relaxation in poly(alkyl methacrylate)s and related polymers probed by photochemical hole burning

Excursion temperature dependences of spectral hole profiles in photochemical hole burning for free-base systems porphyrin/poly(alkyl methacrylate)s are investigated to see the relationship between relaxation properties and chemical structure of the polymers. The irreversible change in hole width is a characteristic of each polymer and is very similar to the relaxation behavior measured mechanically and dielectrically. Poly(methyl methacrylate) (PMMA) shows the highest thermal stability of hole profiles among the polymers presently studied with no marked appearance of local relaxation at 20–100 K. Poly(ethyl methacrylate) (PEMA) and poly(isopropyl methacrylate) (PiPMA) show an increase in hole width even at 20 K with a plateau region at 50–70 K, which is attributed to the rotation of the ethyl or isopropyl group around the C O bond. Polymers which contain more than two serial methylene groups in the side chains (poly(propyl methacrylate), poly(butyl methacrylate), poly(isobutyl methacrylate)) show a similar relaxation behavior around 50–60 K, suggesting the onset of the rotation of the terminal ethyl or isopropyl group in the ester side chain around the C C bond. Low-density polyethylene (LDPE) shows a similar excursion-temperature dependence probably due to the existence of branched oligomethylene side chains. The relaxation behavior is independent of the nature of chromophores, which indicates that irreversible hole broadening is controlled mainly by the local motion of the host matrices.     

Diffusion of anti-tumor drugs through membranes from hydrophilic methacrylate gels

Permeation parameters of four anti-tumor drugs across membranes prepared from hydrophilic methacrylate gels were measured and compared with the permeation of NaCl. It was found that by increasing the ratio of butyl methacrylate (BMA) to hydroxyethyl methacrylate (HEMA), the rate of diffusion can be lowered to practically zero at 20% BMA. However, this decrease is different with various drugs due to the interaction of the drug with the gel. Differences by a factor of two were found in our set of drugs. Therefore, each new drug should be tested in this way. In addition a routine testing of dialysing devices by an NaCl solution is suggested as a method for detecting technological imperfections and calibrating the deviations from standard parameters. A chemical modification of the membrane is recommended as the best way for controlling the permeation rate.     

New thermo-crosslinking reactions of copolymers of phenyl methacrylates by use of polyfunctional epoxy compounds

Successful new thermo-crosslinking reactions of copolymers of various phenyl methacrylates by use of polyfunctional epoxy compounds were carried out in the film state at 100–150°C in presence of quaternary ammonium salts, quaternary phosphonium salts, tert-amines, or the crown ether dicyclohexyl-18-crown-6/potassium salt systems as a catalyst. Addition reactions of 4-nitrophenyl, 4-chlorophenyl or phenyl ester groups in the copolymers with ethylene glycol diglycidyl ether (EGGE) result in gel compounds without other side reactions. The rate of gel production of the copolymer having electron-attracting groups such as the 4-nitro group on phenoxide is faster than that of the other copolymers. It was also found that the rate of gel production of the copolymer is affected by the amount of phenyl methacrylate component in the copolymer, the glass transition temperature (T_g) of the copolymer, the structure of polyfunctional epoxy compounds as a crosslinking reagent, the length of alkyl chain in the catalyst, and the kind of counter anion of the catalysts, respectively.     

Preparation of poly(ethylene glycol)-block-poly(caprolactone) copolymers and their applications as thermo-sensitive materials

The polymerization of epsilon-caprolactone (epsilon-CL) was initiated by the terminal alcohol of methoxy poly(ethylene glycol) (MPEG) as an initiator via activated ring-opening polymerization in the presence of HCl. Et2O as a monomer activator. The molecular weights of the poly(epsilon-caprolactone) (PCL) in MPEG-PCL diblock copolymers controlled with the feed ratio of epsilon-CL to MPEG. The polymerization was preceded by living fashion with no termination or chain transfer. This polymerization procedure offered MPEG-PCL diblock copolymers with well-defined structures. The gel-to-sol transitions of MPEG-PCL diblock copolymer solutions were also examined. The diblock copolymers synthesized with various MPEG and PCL lengths were dissolved in water at 80 degrees C in various concentrations. The polymer solutions formed gel at room temperature. The formed gel became fluids again by increasing the temperature. The gel-to-sol transition showed strong dependence on the length of the MPEG and PCL diblock segments. When the polymer solution was injected into rat, it became a gel at body temperature. The formed gel maintained for 1 month. We confirmed that MPEG-PCL diblock copolymers with well-defined structures served as new thermo-sensitive biomaterials.     

Effect of molecular weight and polydispersity on kinetics of dissolution and release from ph/temperature-sensitive polymers

N-isopropylacrylamide (NIPAAm) polymers exhibit a lower critical solution temperature (LCST). Aqueous solutions of these polymers are soluble below their LCST and precipitate above their LCST. The LCST is dependent on pH for polymers with ionizable groups because of a change in hydrophilicity with ionization and electrostatic repulsion that cause a shift in the LCST. We have designed a novel polymeric delivery system that utilizes linear, pH/temperature-sensitive terpolymers of NIPAAm, butyl methacrylate (BMA) and acrylic acid (AA). This system allows the aqueous loading of drugs in polymeric beads with high loading efficiency while preserving the bioactivity of the protein drug. Furthermore, the unique properties of the pH/temperature-sensitive polymeric bead make it a potential system for oral drug delivery of peptide and protein drugs to different regions of the intestinal tract. This study aims at investigating the effect of polydispersity and molecular weight (MW) of terpolymers of poly(NIPAAm-co-BMA-co-AA) with feed mol ratio of NIPAAm/BMA/AA 85/5/10 on the polymer dissolution rate and on the release kinetics of a model protein, namely insulin. Varying the weight average MW (Mw) and polydispersity of the polymer modulated the polymer dissolution rate and the release rate of insulin from pH/temperature-sensitive polymeric beads. An increase in the polydispersity of the polymer through the addition of high MW polymer chains caused a decrease in the release rate of insulin and in the polymer dissolution rate. High MW polymer chains impose a certain degree of interaction between polymer chains due to chain entanglement. There is a limiting value of MW above which chain entanglement has no effect on drug release rate.     

Synthesis,characterization and controlled drug release from temperature-responsive poly(ether-urethane) particles based on PEG-diisocyanates and aliphatic diols

A series of linear amphiphilic poly(ether-urethane)s with alternative hydrophilic/hydrophobic segments based on PEG-diisocyanates and aliphatic diols is developed. The molecular structures of the copolymers were confirmed with nuclear magnetic resonance, Fourier transform infrared spectra and gel permeation chromatography. Nanoparticles prepared by self-assembly of the resulting copolymers show sharp temperature-responsive phase transition. The phase transition temperature could be easily modulated by the length of hydrophilic or hydrophobic segments of the polymer. The mechanism of the temperature-responsive behaviour is discussed. In the presence of these obtained poly(ether-urethane)s, doxorubicin (DOX) could be dispersed into aqueous solution. The ratio of DOX release from polymeric particles increased sharply above the phase transition temperature, while the release was suppressed below the phase transition temperature. A controlled drug release can be achieved by changing the environmental temperature. The easy-prepared polymeric nanoparticles, with features of biocompatibility, biodegradability and tail-made temperature responsiveness, are a kind of promising carriers for temperature-controllable drug release.     

Gas-to-liquid permeation in silicon-containing, crosslinked, glassy copotymers of methyl methacrylate

Copolymers of methyl methacrylate with disiloxane derivatives have been proposed as biomaterials for contact lens applications. Although glassy, these copolymers exhibit high oxygen permeability and adequate wettability so that they can be used for manufacture of hard, extended wear lenses. CrossHnked copolymers of poly(methyl methacrylate-co-1,3-bis(methacryloxymethyl)-1,1,3,3-tetramethyl-disiloxane), P(MMA-co-BMTDS), containing from 0.085 to 0.53 mole fraction of BMTDS were prepared and tested for oxygen permeation using a novel apparatus which simulates the atmosphere/lens/cornea conditions. The gas-to-liquid dissolved oxygen permeability, P_gd, was determined and it was found to increase with BMTDS content Permeability values for P(MMA-co-BMTDS) at 34°C were significantly higher than for pure homopolymer PMMA, although these copolymers were glassy at this temperature. The increased oxygen permeation was attributed to increased oxygen solubility in the copolymers due to the presence of the -Si-0-bonds.