N-methylol Acrylamide Research Articles

Preparation and characterization of poly (N-methylol acrylamide)/polyethylene glycol composite phase change materials for thermal energy storage

The cross-linked poly (N-methylol acrylamide)/polyethylene glycol (PN-MA/PEG) with an interpenetrating polymer network (IPN) was prepared by emulsion polymerization as composite phase change material (CPCM). N, N′-methylene bisacrylamide (MBA) was used for crosslinking agent. The prepared CPCM was characterized by Fourier Transform Infrared (FT-IR) spectroscopy, X-ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), thermal cycle test, Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). FT-IR results stated that there is no chemical interaction between PEG and PN-MA. XRD results indicated that the introduction of PN-MA did not change the crystal type of PEG. PEG still exhibits crystallization behavior under the constraints of cross-linked PN-MA. The DSC results indicated that CPCM melts at 26.24 °C with a latent heat of 106.5 J/g and solidifies at 32.56 °C with a latent heat of 104.9 J/g. The TGA results indicated that the CPCM has good thermal stability and is suitable for thermal energy storage application. The results of thermal cycle test indicated that the macroscopic morphology and latent heat of CPCM were almost unchanged after 40 thermal cycles. SEM and TEM results indicated that the microscopic morphology of CPCM was spherical and the particle size distribution was around 145 nm.

Alkaline monomer for mechanical enhanced and self-healing hydrogels based on dynamic borate ester bonds

Hydrogels based on borate ester bonds enable fast, multiple repairs with their dynamically reversible covalent bonds at room temperature. However, these materials could only be healed with alkaline additives to control the pH values right now which results in the limited healing and mechanical performance. In this research, dimethylaminoethyl methacrylate (DMAEMA) is employed as an alkaline monomer and randomly copolymerize with N-methylol acrylamide (NAM) to form a mechanical enhanced and self-healing hydrogel at room temperature. The hydrogels exhibit a dramatic fracture stress of as much as 368 kPa and fracture strain of 542%. Besides, the anti-fatigue properties of the hydrogels (slight residual deformation after stretch-release cycles at strain of 200%) have been proved as well. Moreover, the as-prepared hydrogels successfully achieve 91% of the fracture stress recovery within 1 h at room temperature and 100% repair of the fracture strain after 24 h. At last, the healing mechanism has been discussed. This work provides a novel system for the borate ester bonds-based self-healing materials with improved healing and mechanical performance by the simple and efficient method which would expand the range of applications in smart materials.

Preparation of Silicone-Modified Acrylate Latex and its Application for Low-Emission Printing of PET Fibre

Abstract Attempts were made to find a more environmentally friendly technique for the printing of polyester (PET ) fabric, acting as an alternative to a usual disperse dye direct-printing process by using a plenty of water and salt and producing effluent contaminants. The low-emission printing technique includes the recipe containing disperse dye paste, synthetic thickener and the water-based silicone-modified acrylate and high-temperature curing process. The water-based silicone-modified acrylate for adhesive coating of polyester (PET) fibres was synthesized using butyl acrylate (BA), eight four methyl siloxane (D4), acrylonitrile (AN), styrene (St), methyl acrylic acid (MAA) and N-methylol acrylamide (NMA).The results showed that the silicone-modified acrylate adhesive could increase the percentages of dye fixation and the colour strength. The superior colour fastness (≥level 4) with the low-emission printing process was realized. The wastewater stream produced by the technique had a residual dye concentration of 2.62 mg/L, which was reduced by approximately 19 times that produced by traditional direct printing. The effluent wastewater drainage was reduced by 76.9%.

A metal organic framework polymer monolithic column as a novel adsorbent for on-line solid phase extraction and determination of ursolic acid in Chinese herbal medicine

A metal organic framework (MOF)-polymer monolithic column was prepared by redox initiation using modified MOF and N-methylolacrylamide (NMA) as co-monomers. The obtained monolithic column was characterized by scanning electron microscopy (SEM) and nitrogen adsorption-desorption isotherm measurement. It was used as a solid phase extraction (SPE) absorbent for the online enrichment of ursolic acid (UA) by high performance liquid chromatography. The adsorption amount of UA on the monolith was compared with that of silica gel-C18 adsorbent and the monolith without MOF material. The MOF-polymer monolithic column showed high selectivity and good permeability. Under the optimum conditions for extraction and determination, the calibration equation was y = 79.854× + 0.1939; the linear range was 0.001–0.9 mg/mL; the linear regression coefficient was 0.9993; the limit of detection (LOD) and the limit of quantification (LOQ) were 0.17 μg/mL and 0.57 μg/mL, respectively; the inter-day and intra-day accuracies were <6.44%; the recovery was in the range of 86.52–105.26%. The MOF-polymer monolithic column was successfully used as SPE column for enrichment and determination of UA in Chinese herbal medicine.

Study on Properties of a Novel Flame Retardant Epoxy Curing Agent

Using 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10 oxide (DOPO) and N-methylol acrylamide as the main raw materials, the curing agent DOPO-NMA was synthesized. The flame retardant curing agent DOPO-NMA and E-51 epoxy resin (EP) were then cured to obtain epoxy resin E-51 system, and its flame retardancy, thermal stability and mechanical properties were studied. The results showed that the tensile, bending and impact strength of the cured system decreased with the increase of phosphorus mass fraction in the resin system, and the flame retardancy rating, limiting oxygen index (LOI) and char yield at 700°C increased with the increase of phosphorus mass fraction in the resin system.

Thermal crosslinking and fabrication of poly (N-isopropylacrylamide) nanofibers

To prepare thermo-responsive nanofibers with excellent stability and high sensitivity, the copolymer P (NIPAm-co-NMA) is synthesized by free radical copolymerization of N-isopropylacrylamide (NIPAm) and N-methylol acrylamide (NMA). Furthermore, the polymer is crosslinked via thermal treatment which results in highly cross-linked copolymer, thereby increasing the resistance to dissolution around lower critical solution temperature (LCST). In addition, the copolymer is electrospun into nanofibers. The influence of electrospinning condition on the morphology and diameter of the resulting nanofibers, and the effects of thermal treatment temperature and duration on the degree of cross-linking and morphology retaining ability are systematically investigated. The results show that the optimal spinning conditions are as follows: the polymer concentration is 10% and the spinning voltage is 10 kV. The optimal thermal cross-linking temperature is 130 ℃ and the treatment duration is 6 h. The degree of cross-linking of the as-obtained fibers is 82%. The fibers after thermal cross-linking could maintain the stability in water at a low temperature. After 5 cycles of heating-cooling, the fibers could retain 98% of the initial weights.

Preparation, characterization and properties of starch-based adhesive for wood-based panels

A new biodegradable, renewable, and environmentally friendly starch-based adhesive for wood-based panels was synthesized. The synthesis was conducted by grafting polymerization of vinyl acetate (VAC) monomer onto corn starch and crosslinking polymerization with N-methylol acrylamide (NMA). Compared with the traditional starch-based wood adhesive, the water resistance of starch-based adhesive with NMA (SWA-N) was greatly improved to more than 1 MPa; this exceeds the Chinese standard by 40%. The results from various analyses, including particle size, contact angle, thermogravimetric analysis (TGA), Fourier-transform infrared (FTIR), confocal Raman microscopy (CRM) and 13C-CPMAS, indicated that such improved performance is due to increased crosslinking density and formation of complex network structure. Such complex network structure was found to inhibit excessive expansion of the adhesive during high temperature pressing and water absorption. As a result, the internal structure of the adhesive remained intact when subjected to hot pressing and placed in wet conditions.

A novel poly (NMA-co-DEA-co-EDMA) monolithic column as a sorbent for online solid-phase extraction and its application in the determination of β-sitosterol in plant oil samples.

A novel monolithic column was prepared by in-situ free radical polymerization using N-methylolacrylamide (NMA) and N,N-diethylacrylamide (DEA) as co-monomers. The monolith was characterized by scanning electron microscopy (SEM) and its nitrogen adsorption-desorption isotherm, and it was used as a solid phase extraction (SPE) absorbent for the online enrichment of β-sitosterol by high performance liquid chromatography. The optimized method had good linearity, and the linear regression coefficient was 0.998. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.006 mg/mL and 0.02 mg/mL, respectively. The interday and intraday accuracies were less than 7.28%. The spiked recoveries of β-sitosterol in the six plant oil were 90.96-103.56%. The maximum amount of β-sitosterol adsorbed on the monolithic column was 12.69 mg/g, and the enrichment factor of β-sitosterol was 78. The results showed that the monolith could be used as an online SPE absorbent for the determination of β-sitosterol in plant oil samples.

Simultaneous Determination and Enrichment of β-Sitosterol From Edible Oil Samples Using Poly(NMA-ST-co-TAIC-co-EDMA) Monolith as Sorbent with On-line SPE-HPLC

A poly(NMA-ST-co-TAIC-EDMA) monolithic column was prepared by redox initiation method using N-methylolacrylamide (NMA) and styrene (ST) as co-monomers. The composite monolith was characterized by scanning electron microscopy (SEM) and nitrogen adsorption–desorption isotherm and was used as a solid phase extraction (SPE) absorbent for enrichment of β-sitosterol by high performance liquid chromatography (HPLC). Under the optimum conditions for extraction and determination, the calibration equation was y = 1.02247x + 0.1766; the linear range was 0.015–0.75 mg mL−1 and the linear regression coefficient was 0.998. The limit of detection (LOD) and the limit of quantification (LOQ) were 0.006 mg mL−1 and 0.02 mg mL−1, respectively. The spiked recoveries of β-sitosterol in edible oil samples were 83.60–103.88%; precisions for intra-day and inter-day assays presented as relative standard deviations were less than 6.0% and 6.2%, respectively. The enrichment factor of β-sitosterol was 60 and the results showed that the monolithic column had high selectivity and good permeability as an on-line SPE absorbent for the enrichment and determination of β-sitosterol from edible oils.

Facile synthesis of Cu-BDC/Poly(N-methylol acrylamide) HIPE monoliths via CO2-in-water Emulsion stabilized by metal-organic framework

Macroporous poly(N-methylol acrylamide)–high internal phase emulsion [poly(NMA)HIPE] composite monoliths were prepared by carbon dioxide-in-water (CO2/W) emulsions using metal-organic framework (MOF) Cu-BDC (BDC = 1,4-dicarboxybenzene) as stabilizer. The composite monoliths were characterized using XRD, SEM, EDS-mapping, FT-IR, TG, and mercury injection methods. Increasing the internal phase fraction would lead to the decrease of monolith density and the increase of void size, and it is favorable for the formation of macroporous interconnected structure with low density and porosities up to 81.6%. The mechanical properties of the Cu-BDC/poly(NMA)HIPE and Cu-BDC removal were also evaluated. The composite polyHIPEs exhibited high antibacterial activity against Escherichia coli. The presented approach facilitated the clean manufacture of open-celled MOF based scaffolds in a one-pot process with porosity of up to 82%.

An alginate-based hydrogel composite obtained by UV radiation and its release of 5-fluorouracil

A novel pH-sensitive and macroporous NaAlg-based hydrogels were prepared, the monomers of which were N-methylolacrylamide (NMAAm) and acrylic acid, using N,N-methylene-bis-acrylamide (MBA) as a cross-linker, 2,2-dimethoxy-2-phenylacetophenone as a photoinitiator via ultraviolet irradiation. The morphology, thermal property and structure of hydrogel were characterized by Fourier transform infrared spectroscopy, scanning electron microscope, X-ray diffractometer and thermogravimetric analysis. The swelling ratios (SRs) of hydrogel were investigated in water, salt and pH solutions. The SR of hydrogel in water increased from 8.1 to 19.4 g/g with increase in weight of NaAlg from 0.2 to 1.0. The result indicated that hydrogel displayed favorable pH- and salt-sensitive. 5-fluorouracil (5-FU) as a model drug was loaded on hydrogel, the drug encapsulation efficiency of products reached to 85.2%, and the cumulative release rate of drug was 78.4 and 37% in the intestinal and gastric fluid, respectively. In addition, the dynamic data of drug release were evaluated by different mathematical models, and the experimental results revealed that it was more fitted to Ritger–Peppas and Higuchi equation models, correlation coefficients (R2) of which were up to 0.99.

The effects of feeding ratio on final properties of vinyl acetate-based latexes via semi-continuous emulsion copolymerization

Semi-continuous emulsion polymerization of vinyl acetate and dioctyl maleate (VAc/DOM) (60/40, w/w) was carried out with pre-emulsion feeding using potassium persulfate as an initiator. The influence of emulsifier type and its initial ratio were studied and the mixture of non-ionic emulsifiers; 30 and 10 mol ethoxylated nonylphenol (NP30 and NP10) at a ratio of 50/50 (w/w) provided better pre-emulsion and polymerization stability, and also final latex stability. In addition, two series of experiments were conducted to determine the effect of initiator and reactive surfactant, oligomeric N-methylol acrylamide (o-NMA) amount in the initial reactor charge on the latex properties. By increasing the initial initiator amount from 10 to 50 wt%, the average particle size of the latexes decreased from 203 to 143 nm. As expected, the amount of initiator strongly affected the particle charge and the highest zeta potential value was obtained when 50 wt% of the initiator was initially present in the reactor, showing the increased latex stability. On the other hand, it was detected that the colloidal properties of the copolymer latexes were significantly affected by the change of initial charge of o-NMA. The o-NMA amount exceeding 50 wt% caused coagulation. When all o-NMA was initially fed, the highest viscosity value, 9878 cP; lowest zeta potential value, − 5 mV; and the highest surface tension value, 37.5 mN m−1, were obtained. Consequently, the change in the initial charge of emulsifier, initiator, and reactive surfactant has played an important role on the colloidal stability of VAc/DOM latexes.

Effect of geometry and hybrid adhesive on strength of finger joints of Pinus elliottii subject to humidity and temperature

ABSTRACTThe optimized bonding of glued finger joints is required for structural and nonstructural applications. The use of nonspecific adhesives, combined with the joint geometry and exposure of joints to humidity and temperature, are factors that can compromise the durability of glued joints. The main objective of this study is the development of cross-linking poly(vinyl acetate) (PVAc) hybrid adhesive to produce nonstructural finger joints of Pinus elliottii with finger lengths of 6.5 and 4.5 mm. The adhesives were produced by emulsion copolymerization of vinyl acetate with n-butyl acrylate with different amounts of N-methylol acrylamide and blended with resorcinol-formaldehyde resin (RF) and aluminum chloride (AlCl3). The rheological behavior of adhesives was investigated. We found that the joint configuration and the exposition time employed influenced joint strength. The PVAc/RF adhesive showed a thicker bond line and consequent deeper penetration into the pores of the wood as verified by microscopy analysis. Statistically differences in bond strength of the adhesive joints were found with respect to different conditioning times and finger length. The highest values were exhibited by the joints produced with a finger length of 6.5 mm and glued with the hybrid adhesive (AD-4) than that joints produced with a finger length of 4.5 mm.

Flexible and stretchable polyurethane/waterglass grouting material

Flexibility and stretchability are of ever increasing importance in constructing high-performance grouting materials. Herein, a facile, effective and cost-efficient strategy to make organic-inorganic hybrid chemical grouting material in a “flexible and stretchable” way was based on polymerization of carbon double bond and excellent synergistic interactions among N-Methylol acrylamide, butenediol, waterglass and prepolymer. Upon the optimal percentages of waterglass (44%), N-Methylol acrylamide (3.5%), butenediol (1.5%), Alkylphenol polyoxyethylene (OP-9, 0.5%), 2,2′-azobis[2-(2-imidazolin-2-yl)propane] (0.35%), 2,2-dimorpholinodiethylether (DMDEE, 0.15%) and prepolymer (50%), the obtained polyurethane/waterglass grouting material with three-dimensional interpenetrating network structure displayed an excellent flexibility, satisfactory compressive strength of 13.4MPa at 50% compression state, and relatively large elongation of up to 60% with a stable stretching for 200times. The grouting material was mainly composed of amorphous polyurethane and crystalline polysilicic acid/NaHCO3/Na2CO3 composite, and its probable formation mechanism was proposed. Additionally, the grouting material possessed favorable thermal stability and repairment performance for roadway cracks. This work may open a simple and convenient avenue for the preparation of organic-inorganic hybrid chemical grouting material with flexibility and stretchability.

Preparation and Characterization of Functionalized Chitosan Derivatives from Prawn Waste for Cellulose Fibre Modification to Enhance Textile Properties

The purpose of this research was to develop water soluble textile modifiers based on biopolymer having improved textile properties including tensile strength, moisture absorption, wash resistance, dye-ability and colour fastness properties. Two fibre reactive chitosan derivatives such as N-(2-hydroxy) propyl-3-trimethylammonium chitosan chloride (HTAChC) and N-methylolacrylamide-N-(2-hydroxy) propyl-3-trimethylammonium chitosan chloride (NMAHTAChC) were synthesized from chitosan through dispersion of chitosan with glycidyltrimethylammonium chloride (GTMAC) in aqueous medium and dissolution of HTAChC in aqueous N-methylolacrylamide (NMA) solution in presence of NH4Cl and 4-methoxyphenol, respectively. The physicochemical properties of prepared derivatives were studied and the degree of quaternization (DQ) of HTAChC was 0.94, double bond content of the NMA-HTAChC was 0.926 mmol/g and moisture content of HTAChC and NMA-HTAChC were 22.06% and 18.78%, respectively. The FTIR spectra of HTAChC showed prominent peak at 1480 cm-1 (C-H bending), 1650 cm-1 (C=O group) and that of NMA-HTAChC showed the peaks at 1670 cm-1 (C=O stretch) and 1545 cm-1 (N–H bending) which confirms the synthesized derivatives. The prepared derivatives were further used for modification of cotton and jute fibres Graft yield percent of HTAChC and NMA-HTAChC on cellulose fibre surfaces were 10.69% and 14.74% for jute and 14.56% and 18.86% for cotton, respectively. Grafting was investigated by FTIR, SEM, TGA, DTA and DTG analyses. The surface of modified fibre was investigated by SEM and the surface was smoother than unmodified fibre. The modified fibre showed decreased thermal stability, improved moisture absorption, wash resistances and tensile strength compared to unmodified fibres. It was also observed that textile modifying properties of NMA-HTAChC is better than HTAChC due to higher fibre affinity of NMA-HTAChC to cellulose fibres. Dyeing of modified and unmodified cotton and jute fibres with reactive and direct dyes revealed that dye exhaustions were increased up to 10% due to modification.

Fabrication and characterization of a new enhanced hybrid shell microPCM for thermal energy storage

MicroPCMs (microencapsulated phase-change materials) were successfully synthesized using PMMA (poly(methyl methacrylate)) and UF (urea-formaldehyde) as raw materials for hybrid shells, and n-tetradecane as core materials. NMA (n-methylol acrylamide) with two functional groups of double-bond and hydroxymethyl was used as a crosslinking agent. The morphologies and chemical structures of microPCMs were characterized using scanning electron microscopy (SEM) and Fourier transformed infrared (FTIR) spectroscopy. The agglomerations of the UF/PMMA hybrid samples might be influenced by two factors: cross linking action of NMA and PMMA/UF ratio in shell materials. The phase change properties and thermal durability were investigated by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA), respectively. The UF/NMA/PMMA hybrid shell microcapsules has an enthalpy of 175.5J/g which is higher than the single-layer shell samples of PMMA and UF, and a better leakproofness than the UF/PMMA hybrid samples without NMA owing to the semi-IPN microstructure. Likewise, the UF/NMA/PMMA hybrid samples have higher thermal durability than the single layer shell samples of PMMA and UF and the UF/PMMA hybrid samples without NMA. Moreover, the thermal cycling test of the UF/PMMA hybrid samples with NMA was carried out for 100 heating/cooling cycles and indicated that the developed hybrid shell microPCMs have good chemical stability and thermal reliability. The heating-up experiment revealed that the foam treated by microcapsules had a better thermoregulatory property than the raw foam. Based on the results obtained, it can be concluded that n-tetradecane/UF/PMMA microPCMs have potential thermal energy storage applications.

New corrosion inhibitor acrylamide methyl ether for mild steel in 1 M HCl

Pursuit of good inhibition performance has been a persistent objective for advanced inhibitor industry. Here we demonstrate the experimental realization of a new corrosion inhibitor acrylamide methyl ether (AAME) from N-Methylol acrylamide (N-MAM) for mild steel in 1M HCl. The resultant adsorption films have inhibition efficiency as high as 96.2%. Moreover, a theoretical investigation is also launched to demonstrate the potential mechanism behind the promising corrosion behaviors. This work represents a significant step forward, as it demonstrates how to make scalable AAME inhibitors as well as to enhance inhibition performances for high-efficiency and cost-effective corrosion inhibition platforms.

A strategy of integrating ultraviolet absorption and crosslinking in a single molecule: DFT calculation and experimental

Creation of advanced ultraviolet light absorbers having crosslinking ability has been persistent objective for anti-ultraviolent aging polymers. We present here the integration of 2, 4-dihydroxybenzophenone (UV-0) and N-methylol acrylamide (NMA) for novel ultraviolet absorber namely (3,5-dimethacrylamide-2,4-dihydroxyphenyl) (phenyl)methanone (UV-CA), which is subsequently utilized as a crosslinking agent after suffering Friedel–Crafts reaction. The preliminary results demonstrate that quantum chemical calculations (DFT) is a promising avenue in demonstrating the optimized geometry, charges, energy levels and UV electronic absorption bands of the UV-CA in the singlet (steady and excited states). The structure parameters and natural band orbital (NBO) calculations suggest that the intramolecular hydrogen bond (IMHB) in the UV-0 group is significantly enhanced in comparison to that between UV-0 and NMA groups. The acrylic acid polymers functionalized with UV-CA yield high crosslinking degree and robust UV absorbing performance. The impressive results demonstrate that quantum chemical calculations are promising in organic synthesis to develop advanced compounds.

Isotope Internal Standard Method for Determination of Four Acrylamide Compounds in Food Contact Paper Products and Food Simulants by Ultra-High Performance Liquid Chromatography Tandem Mass Spectrometry

A new method was developed for the determination of four acrylamide compounds (acrylamide, methacrylamide, N-methylol acrylamide, N-(Methoxymethyl)methacrylamide) in food contact paper products, three kinds of water-based food simulants, and dry food simulant (modified polyphenylene oxide, MPPO) by using ultra-high performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Acetonitrile was used as the extraction solvent for different kinds of samples. The extraction solution of paper products was purified with QuEChERS technology. Four analytes were separated by gradient elution in a UPLC HSS T3 column (100 mm × 2.1 mm, 1.8 μm) with methanol and 0.1 % formic acid water as mobile phases, and then detected in electrospray ionization mode of MS/MS with multiple reaction monitoring (MRM). Under the optimal conditions, the calibration curves for four analytes were linear within the range of 1.0–200 μg/L and the correlation coefficients were higher than 0.998. The quantitation limits of the method (S/N = 10) of four analytes were in the range of 0.3–20 μg/kg. The mean recoveries for five sample matrixes at three spiked concentration levels of 0.3–200 μg/kg were in the range of 81–108 % with the relative standard deviations (RSDs, n = 6) values ranging from 2.5 to 7.1 %. The developed method is accurate, simple and rapid, which can be applied to the determination of acrylamide compounds in food contact paper products and food simulants.

Self-crosslinkable complexes based on poly(ethylene glycol) (PEG), poly(itaconic acid) (PIA) and N-methylol acrylamide (NMA) as pharmaceutical hydrophilic matrices

The formation and characterization of poly(itaconic acid)/N-methylol acrylamide/poly(ethylene glycol) (PIA/NMA/PEG) complexes through in situ polymerization of itaconic acid on poly(ethylene glycol) was investigated. FTIR indicated that PEG crystallization was hindered by complex formation. The decrease in the crystallinity of PEG was also observed by DSC and indicated that the mobility of some PEG segments was inhibited by the presence of the polyacid. According to the swelling experiments, complexes proved to be suitable for use as excipient in the preparation of drug delivery systems responsive to pH changing. DMA was used to estimate the crosslink densities and the results were found to be in good agreement with the swelling results. Further, the adhesion strength of the synthesized polymers was used as preliminary evaluation of their potential of mucoadhesion. The results indicated that the adhesion performance is related to the presence of NMA. Drugs which suffer degradation in stomach pH, such as proteins and enzymes are potential candidates to be included in the systems based on PIA/NMA/PEG to pass through the stomach (pH near to 1.2–3.5). Upon reaching the initial portion of the small intestine (pH >5.5), the polymer will swell and release the active substance via diffusion and/or erosion of the matrix.