Improving polyethylene–octene elastomer/chitosan by graftation of acrylic acid onto polyethylene–octene elastomer—mechanical properties and biodegradability examination and composites characterization

In this study, the properties of polyethylene–octene elastomer/chitosan (POE/chitosan) and acrylic acid (AA)‐grafted‐polyethylene–octene elastomer/chitosan (POE‐g‐AA/chitosan) were examined using various characterizing instruments. Mechanical and thermal properties of POE deteriorated noticeably when it was blended with chitosan, due to the unsatisfactory compatibility between the two phases. The greater compatibility of POE‐g‐AA with chitosan, due to the formation of ester carbonyl and imide groups, led to a much better dispersion and homogeneity of chitosan in the POE‐g‐AA matrix and consequently to noticeably better mechanical properties. Furthermore, with a lower melting point temperature, the POE‐g‐AA/chitosan blend was more easily processed than POE/chitosan. POE‐g‐AA/chitosan had a higher water resistance than POE/chitosan. Both blends suffered weight loss when buried in soil, especially at high levels of chitosan substitution, indicating that both were biodegradable. The mechanical properties of both blends, such as tensile strength and elongation at break, also deteriorated after being buried in soil. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3882–3891, 2003     

Characterization and biodegradability of polyester bioplastic-based green renewable composites from agricultural residues

The biodegradability, morphology, and mechanical properties of composite materials consisting of acrylic acid-grafted poly(butylene succinate adipate) (PBSA-g-AA) and agricultural residues (rice husk, RH) were evaluated. Composites containing acrylic acid-grafted PBSA (PBSA-g-AA/RH) exhibited noticeably superior mechanical properties compared with those of PBSA/RH due to greater compatibility with RH. The dispersion of RH in the PBSA-g-AA matrix was highly homogeneous as a result of ester formation, and the consequent creation of branched and cross-linked macromolecules, between the carboxyl groups of PBSA-g-AA and hydroxyl groups in RH. Each composite was subject to biodegradation tests in an Azospirillum brasilense BCRC 12270 liquid culture medium. The bacterium completely degraded both the PBSA and the PBSA-g-AA/RH composite films. Morphological observations indicated severe disruption of the film structure after 20-40 days of incubation. The PBSA-g-AA/RH (20 wt%) films were not only more biodegradable than those made of PBSA but also exhibited lower molecular weight and intrinsic viscosity, implying a strong connection between these characteristics and biodegradability.     

Morphology and thermal properties of poly(L‐lactide)/poly(butylene succinate‐co‐butylene adipate) compounded with twice functionalized clay

Poly(L ‐lactide) (PLLA)/poly(butylene succinate‐co‐butylene adipate) (PBSA) blends were compounded with Cloisite 25A® (C25A) and C25A functionalized with epoxy groups, respectively. Epoxy groups on the surface of C25A were introduced by treating C25A with (glycidoxypropyl)trimethoxy silane (GPS) to produce so called Twice Functionalized Organoclay (TFC). Variation of morphology and properties of PLLA/PBSA/C25A composites was investigated before and after the treatment with GPS. The morphological structure of the composites was analyzed by using X‐ray diffractometry (XRD) and transmission electron microscopy (TEM). The silicate layers of PLLA/PBSA/TFC were exfoliated to a larger extent than PLLA/PBSA/C25A. Incorporation of the epoxy groups on C25A improved significantly elongation at break as well as tensile modulus and tensile strength of PLLA/PBSA/C25A. The larger amount of exfoliation of the silicate layers in PLLA/PBSA/TFC as compared with that in PLLA/PBSA/C25A was attributed to the increased interfacial interaction between the polyesters and the clay due to chemical reaction. Thermo gravimetric analysis revealed that both T_5%, which was the temperature corresponding to 5% weight loss, and activation energy of thermal decomposition of PLLA/PBSA/TFC were far superior to those of PLLA/PBSA/C25A as well as to those of PLLA/PBSA, indicating that the composites with exfoliated silicate layers were more thermally stable than those with intercalated silicate layers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 478–487, 2005     

Improved antibacterial properties of an Mg‐Zn‐Ca alloy coated with chitosan nanofibers incorporating silver sulfadiazine multiwall carbon nanotubes for bone implants

Bacteria‐caused infection remains an issue in the treatment of bone defects by means of Mg‐Zn‐Ca alloy implants. This study aimed to improve the antibacterial properties of an Mg‐Zn‐Ca alloy by coating with chitosan‐based nanofibers with incorporated silver sulfadiazine (AgSD) and multiwall carbon nanotubes (MWCNTs). AgSD and MWCNTs were prepared at a weight ratio of 1:1 and then added to chitosan at varying concentrations (ie, 0, 0.25, 0.5, and 1.5 wt.%) to form composites. The obtained composites were ejected in nanofiber form using an electrospinning technique and coated on the surface of an Mg‐Zn‐Ca alloy to improve its antibacterial properties. A microstructural examination by scanning electron microscopy (SEM) revealed the diameter of chitosan nanofiber ejected increased with the concentration of AgSD‐MWCNTs. The incorporation of AgSD‐MWCNTs into the chitosan nanofibers was confirmed by Fourier transform infrared spectroscopy (FTIR). Examination of the antibacterial activity shows that chitosan nanofibers with AgSD‐MWCNTs can significantly inhibit the growth and infiltration of Escherichia coli and Staphylococcus aureus. Biocompatibility assay and cell morphology observations demonstrate that AgSD‐MWCNTs incorporated into nanofibers are cytocompatible. Taken together, the results of this study demonstrate the potential application of electrospun chitosan with AgSD‐MWCNTs as an antibacterial coating on Mg‐Zn‐Ca alloy implants for bone treatment.     

Study on superabsorbent composite—VII. Effects of organification of attapulgite on swelling behaviors of poly(acrylic acid‐co‐acrylamide)/sodium humate/organo‐attapulgite composite

A novel multifunctional superabsorbent composite from acrylic acid (AA), acrylamide (AM), sodium humate (SH) and organo‐attapulgite (organo‐APT), PAA‐AM/SH/organo‐APT, was synthesized by aqueous solution polymerization, using N,N′‐methylenebisacrylamide (MBA) as a crosslinker and ammonium persulfate (APS) as an initiator. The organification of APT with hexadecyltrimethyl ammonium bromide (HDTMABr) was proved by FT‐IR. The effects of organo‐APT (HDTMA‐APT) content in the superabsorbent composite and organification degree of it on water absorbency of the superabsorbent composite were studied. The effects of incorporated HDTMA‐APT on swelling rate, water absorbency in various saline solutions and reswelling capability of the superabsorbent composite were also investigated. The results indicate that organification of APT had a remarkable influence on swelling behaviors of the superabsorbent composites. Comparing with the composite doped with APT, water absorbency for the composite incorporated with 10 wt% HDTMA‐APT was enhanced from 996 to 1282 g g^?1 in distilled water and from 63 to 68 g g^?1 in 0.9 wt% NaCl solution, respectively. The superabsorbent composite acquired its highest water absorbency when the organification degree of APT was 8.02 wt%. Water absorbency of the composites in various saline solutions decreased with the increasing concentration, especially for the multivalent cations. In addition, swelling rate and reswelling capability of the superabsorbent composite were also improved by introducing HDTMA‐APT into the composite compared with that of incorporating APT. Copyright © 2006 John Wiley & Sons, Ltd.     

Syntheses and properties of superabsorbent composites based on natural guar gum and attapulgite

Utilization of raw materials available in nature and their application to derive other useful products without any adverse impact on the environment has long been a desired goal. In this work, guar gum (GG) and attapulgite (APT) clay were used as raw materials for preparing guar gum‐g‐poly(acrylic acid)/attapulgite (GG‐g‐PAA/APT) superabsorbent composites through the graft copolymerization of GG, partially neutralized acrylic acid (AA) and APT in aqueous solution. The effects of reaction conditions such as concentrations of the initiator and crosslinker, APT content, etc. on water absorbency were investigated. The composite prepared under optimal conditions gave the best absorption of 529 g/g sample in distilled water and 61 g/g sample in 0.9 wt% NaCl solution. Swelling behaviors revealed that the superabsorbent composites retained a high water absorbency over a wide pH range of 4–11, and the developed composites also exhibited improved reswelling and water‐retention capabilities. The superabsorbent composites can be utilized as eco‐friendly water‐manageable materials for agricultural and horticultural applications. Copyright © 2008 John Wiley & Sons, Ltd.     

Surface properties of chitosan composites with poly(<Emphasis Type="Italic">N</Emphasis>-vinylpyrrolidone) and montmorillonite

Surface properties of composites containing chitosan (Ch) with poly(N-vinylpyrrolidone) (PVP) and montmorillonite (MMT) additives were investigated by contact angle measurements, thermogravimetric analysis (TGA), atomic force microscopy (AFM) and tensile tests. Composites were obtained by drop casting suspensions of montmorillonite (1 wt % relative to chitosan) and polymer (1 wt %) in 0.1 mol/dm³ acetic acid. Contact angle measurements for diiodomethane (D) and glycerol (G) on the surfaces of the chitosan films, PVP and their composite films were made; surface free energies were also calculated. It was found that the PVP/MMT or Ch/PVP/MMT blend surface is enriched with a high surface energy component, i.e., polyvinylpyrrolidone. The roughness of chitosan composites increases after the addition of montmorillonite; this may indicate an increase in the heterogeneity of this composition in comparison to other compositions. The TGA thermograms and mass loss percentages at different decomposition temperatures showed that the thermal stability of the binary composite slightly increases upon the addition of polyvinylpyrrolidone. The mechanical properties such as tensile strength and Young modulus depend on the composition and varied non-uniformly.     

Polypyrrole/poly(N‐isopropylacrylamide‐co‐acrylic acid) thermosensitive and electrically conductive composite microgels

The electrically conductive polypyrrole/dodecylbenzene sulfonic acid/poly(N‐isopropylacrylamide‐co‐acrylic acid) (PPy/DBSA/poly(NIPAAm‐co‐AA)) composite microgels were synthesized by a chemical oxidation of pyrrole in the presence of DBSA as the primary dopant, and poly(NIPAAm‐co‐AA) microgels as the polymeric codopant and template, in which APS was used as the oxidant. It was proposed to prepare “intelligent” polymer microgel particles containing both thermosensitive and electrically conducting properties. The polymerization of pyrrole took place directly inside the microgel networks, leading to formation of composite microgels and the morphology was observed by transmission electron microscope. PPy particles interacted strongly with microgels, as the acid groups of microgels acted as the polymeric codopant. The composite microgels thus formed showed electrically conducting behavior dependent on humidity and temperature. At temperatures lower than lower critical solution temperature, the conductivity decreased with increasing the humidity and a small hysteresis phenomenon was observed. The hysteresis became indistinct when temperature was near volume phase transition temperature. However, after the treatment of high temperature and high humidity, the conductivity increased surprisingly due to the structure reorganization inside the composite microgels. The distinctive functionality of the PPy composite microgels was expected to be utilized in many attractive applications. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1648–1659, 2006     

Mechanical and flame‐retardant properties and thermal decomposition of vinyl ester resin modified by different phenyl silsesquioxanes

The mechanical properties and fire resistance of vinyl ester resin (VER) composites containing cage‐shaped octaphenyl silsesquioxane (OPS), incompletely cage‐shaped phenyl silsesquioxane (PhT₇POSS), and ladder‐shaped phenyl silsesquioxane (PPSQ) were investigated. The POSS structure and dispersion have a great influence on the mechanical properties, thermal stability, and decomposition process of VER composites. The bending strength at break and modulus of the VER‐POSS composites were enhanced obviously, especially for VER‐PPSQ composite and VER‐OPS composite, respectively. In addition, PhT₇POSS‐based VER composites revealed the lower values of the peak heat release rate, total heat release, and total smoke release in cone calorimetry tests due to the formation of dense carbon/silica protective layers that acted as a barrier to heat and mass transfer. Moreover, the flame‐retardant mechanisms of condensed phase and gas phase were also investigated in detail. These results illustrate VERs modified by OPS, PhT₇POSS, and PPSQ are providing an applicable method to fabricate the composites with excellent flame‐retardant and mechanical properties.     

Cellulose/chitosan composites prepared in ethylene diamine/potassium thiocyanate for adsorption of heavy metal ions

Cellulose/chitosan composites were successfully prepared in a new and basic-based solvent system, ethylene diamine/potassium thiocyanate (EDA/KSCN), by dissolving cellulose and chitosan in 70/30 (w/w) EDA/KSCN at ?19 °C, and then coagulating in methanol. Wide angle X-ray diffraction studies revealed that the EDA/KSCN solvent system is capable of disrupting the hydrogen bonds in both cellulose and chitosan and increase the amorphous regions. Stability tests proved that the composites are stable in acidic aqueous solution due to the hydrogen bonds formed between cellulose and chitosan. This is the first time to dissolve chitosan in a basic-based solvent system and prepare cellulose/chitosan composites in a straightforward way. The adsorption of heavy metal ions (Cu²⁺, Cd²⁺, and Pb²⁺) onto the cellulose/chitosan composites was investigated. The adsorption capacity is highly dependent on pH and the maximum metal uptake was obtained at pH 5.0. Increasing initial metal concentration enhanced the diffusion of metal ions to the composite surface and therefore the metal removal efficiency. Higher percentage of chitosan in the composites also led to higher metal adsorption. The results indicated that the prepared cellulose/chitosan (1:1) composite can adsorb 0.53 mmol/g Cu²⁺, 0.28 mmol/g Cd²⁺ and 0.16 mmol/g Pb²⁺ ions at pH 5.0. The Freundlich model and the pseudo-second-order model were in good agreement with the adsorption isotherms and kinetics, respectively. X-ray photoelectron spectroscopy studies indicated that the binding of heavy metal ions is attributed to the nitrogen atoms of amino groups in chitosan. The composites can be reused for metal removal.     

Synergistic effects of β‐cyclodextrin containing silicone oligomer on intumescent flame retardant polypropylene system

The effects of β‐cyclodextrin containing silicone oligomer(CDS), as a synergistic agent, on the flame retardancy and mechanical properties of intumescent flame retardant polypropylene composites were studied by adding different amounts of CDS in intumescent flame retardants. The limiting oxygen index (LOI), UL‐94 test, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were utilized to evaluate the synergistic effects of CDS in the composites. It was found that after a little amount of CDS partially replaced a charring‐foaming agent (CFA) in IFR, LOI values of the composites were enhanced and they obtained a UL‐94 V‐0 rating. IFR system containing 6.25wt% CDS presented the best flame retardancy in PP. The experimental results obtained from LOI and UL‐94, TGA, SEM, and mechanical properties indicated that the combination of CDS and CFA presents synergistic effects in flame retardancy, char formation, and mechanical properties of the composites. This is probably due to different structures of polyhydroxyl macromolecules (CDS and CFA), the existence of dimethyl silicone group in CDS, and the toughness of epoxy silicon chain in CDS. SEM results proved that the interfacial compatibility between IFR and PP was improved by CDS. Copyright © 2009 John Wiley & Sons, Ltd.     

Wet 3‐D printing of epoxy cross‐linked chitosan/carbon microtube composite

Over the last decays, the use of conductive biopolymer composites has been growing in areas such as biosensors, soft robotics, and wound dressing applications. They are generally soft hydrophilic materials with good elastic recovery and compatible with biological environments. However, their application and removal from the host are still challenging mainly due to poor mechanical strength. This work displays a technique for the fabrication of complex‐shaped conductive structures with improved mechanical strength by wet three‐dimensional (3‐D) printing, which uses a coagulation bath to quickly solidify an epoxy cross‐linked chitosan/carbon microtube composite ink. The fabricated conductive structure demonstrated higher elongation strength and improved elastic stability upon the introducing of polypropylene glycol diglycidyl ether (PPGDGE) as the epoxy cross‐linker, which can be due to the formation of networks between oxiran groups of PPGDGE and chitosan amino groups.     

Synthesis and Characterization of Polyindole/Poly(vinyl acetate) Conducting Composites

Composites of a polyindole (PIN) and poly(vinyl acetate) (PVAc) were prepared chemically using FeCl₃ as an oxidant agent in anhydrous media. The composite compositions were altered by varying the indole monomer during preparation. The composites were characterized by FTIR and UV‐visible spectroscopies, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), stress‐strain experiments and conductivity measurements. Moreover, the film of PVAc and PIN/PVAc composites were prepared by casting on glass Petri dishes to examine their stress‐strain properties. PIN/PVAc composites are thermally more stable than PIN. It was found that the conductivities of PIN/PVAc composites depend on the indole content in the composites.     

Composites of poly(L‐lactide‐trimethylene carbonate‐glycolide) and surface modified SBA‐15 as bone repair material

This work aims to develop novel composites from a poly(L ‐lactide‐co‐trimethylene carbonate‐co‐glycolide) (PLTG) terpolymer and mesoporous silica (SBA‐15) nanofillers surface modified by post‐synthetic functionalization. SBA‐15 first reacts with a silane coupling agent, γ‐aminopropyl‐trimethoxysilane to introduce ammonium group. PLLA chains were then grafted on the surface of SBA‐15 through ammonium initiated ring‐opening polymerization of L ‐lactide. Composites were prepared via solution mixing of PLTG terpolymer and surface modified SBA‐15. The structures and properties of pure SBA‐15, γ‐aminopropyl‐trimethoxysilane modified SBA‐15 (H₂N‐SBA‐15), PLLA modified SBA‐15 (PLLA‐NH‐SBA‐15), and PLTG/PLLA‐NH‐SBA‐15 composites were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, transmission electron microscopy, N₂ adsorption‐desorption, differential scanning calorimetry, contact angle measurement, and mechanical testing. The results demonstrated that PLLA chains were successfully grafted onto the surface of SBA‐15 with grafting amounts up to 16 wt.%. The PLTG/PLLA‐NH‐SBA‐15 composites exhibit good mechanical properties. The tensile strength, Young's modulus, and elongation at break of the composite containing 5 wt.% of PLLA‐NH‐SBA‐15 were 39.9 MPa, 1.3 GPa, and 273.6%, respectively, which were all higher than those of neat PLTG or of the composite containing 5 wt.% of pure SBA‐15. Cytocompatibility tests showed that the composites present very low cytotoxicity.     

Effect of nano‐modified SiO2/Al2O3 mixed‐matrix micro‐composite fillers on thermal,mechanical, and tribological properties of epoxy polymers

Thermo‐mechanically durable industrial polymer nanocomposites have great demand as structural components. In this work, highly competent filler design is processed via nano‐modified of micronic SiO₂/Al₂O₃ particulate ceramics and studied its influence on the rheology, glass transition temperature, composite microstructure, thermal conductivity, mechanical strength, micro hardness, and tribology properties. Composites were fabricated with different proportions of nano‐modified micro‐composite fillers in epoxy matrix at as much possible filler loadings. Results revealed that nano‐modified SiO₂/Al₂O₃ micro‐composite fillers enhanced inter‐particle network and offer benefits like homogeneous microstructures and increased thermal conductivity. Epoxy composites attained thermal conductivity of 0.8 W/mK at 46% filler loading. Mechanical strength and bulk hardness were reached to higher values on the incorporation of nano‐modified fillers. Tribology study revealed an increased specific wear rate and decreased friction coefficient in such fillers. The study is significant in a way that the design of nano‐modified mixed‐matrix micro‐composite fillers are effective where a high loading is much easier, which is critical for achieving desired thermal and mechanical properties for any engineering applications. Copyright © 2016 John Wiley & Sons, Ltd.     

Preparation of polymer hollow microspheres covered by polymer solid particles via two polymerization steps

A novel surface modification method for titania nanoparticles is provided via the surface‐initiated photocatalytic polymerization with the aid of acrylic acid (AA) or sodium styrene sulfonate (NaSS). The properties of modified titania nanoparticles are investigated with aqueous electrophoresis measurements, dynamic light scattering (DLS), and transmission electron microscopy (TEM). Then the modified titania is used as Pickering stabilizer for further polymerization and the morphology of the resulted polymer microspheres is characterized by TEM and field‐emission scanning electron microscopy. It is proven that the addition of AA or NaSS for the surface‐initiated polymerization can obviously affect the structure and morphology of the final polymer composite microspheres. The formation mechanism of several kinds of polymer particles is also proposed. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Maleated glycidyl 3‐pentadecenyl phenyl ether with styrene: synthesis and application as compatibilizer in SBR/silica composite

Maleated glycidyl 3‐pentadecenyl phenyl ether with styrene (MGS) was synthesized from glycidyl 3‐pentadecenyl phenyl ether (GPPE), maleic anhydride (MAH) and styrene (St) in the presence of AIBN initiator at 80°C, and then the resultant MGS was applied as a compatibilizer to prepare SBR/silica composites. Meanwhile, the commercial compatibilizer bis‐(triethoxysilylpropyl) tetrasulfide (named Si69) added into composite was also prepared for comparison purpose. The synthetic MGS structure was characterized by GPC and FTIR, and SBR/silica compounds with different compatibilizer were analyzed using RPA, DMA and so on. The results showed that M?n and M?w of MGS were 19,538 g/mol and 23,790 g/mol, respectively. The curing time of compounds with MGS increased, whereas the maximum and minimum torques decreased. The addition of MGS decreased Payne effect of SBR/silica compounds, which implied an improvement of silica dispersion in the compounds. Bound rubber content of compound with MGS was about 1.7 times higher than the absence and 1.5 times higher than that with Si69. The tensile strength of the composites was improved by increasing compatibilizer loading, and the optimum value was observed at 6 phr of MGS. Meanwhile the use of MGS can improve the anti‐aging property of composite. According to DMA, the tanδ value at 0°C of composite with MGS was higher than composite without compatibilizer suggesting that MGS can improve the wet skid resistance of composite. The SEM analysis revealed that introduction of MGS enhanced the compatibility between SBR and silica. Copyright © 2015 John Wiley & Sons, Ltd.     

Preparation of flame‐retardant polyamide 6 by incorporating MgO combined with g‐C3N4

Flame‐retardant polyamide 6 (PA6) was prepared by an inorganic‐organic composite (MCN or MgO/g‐C₃N₄) synthesized by incorporating magnesium oxide (MgO) combined with graphitic carbon nitride (g‐C₃N₄). As compared to g‐C₃N₄, MCN possessed a laminate structure, more holes, and a larger specific surface area. The addition of MCN could effectively improve the flame retardancy and mechanical properties of PA6 due to its better compatibility and dispersion in the PA6 matrix. When the addition of MCN was 20 wt%, the vertical combustion performance of the PA6/MCN sample reached flammability rating V‐0 (UL‐94) and the limiting oxygen index (LOI) was up to 32.1%. The results of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) revealed that the introduction of MCN efficiently enhanced thermal stability of PA6. The morphologies of the char residue observed by scanning electron microscopy (SEM) verified that MCN promoted the formation of sufficient, compact, and homogeneous char layers on the composite's surface during burning. Thus led to increase the char layer strength and improve the flame retardancy of PA6. The thermogravimetric analysis/infrared (TG‐IR) revealed the gas‐phase retardancy mechanism of MCN. Compared with PA6/g‐C₃N₄, PA6/MCN showed better mechanical properties in terms of flexural strength and tensile strength.     

Effect of sunlight on the preparation and properties of cellulose/silver nanoparticle composite films by in situ method using Ocimum sanctum leaf extract as a reducing agent

Cellulose/silver nanoparticle composite films with in situ-generated silver nanoparticles (AgNPs) were prepared using Ocimum sanctum leaf extract as a reducing agent in the absence and presence of sunlight and were characterized by SEM, FTIR, XRD, and antibacterial tests. Sunlight hastened up the preparation of these composite films. The average size of the in situ-generated AgNPs was reduced by the sunlight. The antibacterial activity and other properties of the composites were enhanced by the sunlight. The cellulose/AgNP composite films with improved properties by sunlight can be considered for medical purpose as antibacterial dressing materials.     

Synthesis and properties of chitosan‐based thermo‐ and pH‐responsive nanoparticles and application in drug release

In this research, thermo‐ and pH‐responsive nanoparticles with an average diameter of about 50–200 nm were synthesized via the surfactant‐free emulsion polymerization. The thermal/pH dual responsive properties of these nanoparticles were designed by the addition of a pH sensitive monomer, acrylic acid (AA), to be copolymerized with N‐isopropylacrylamide (NIPAAm) in a chitosan (CS) solution. The molar ratio of CS/AA/NIPAAm in the feed was changed to investigate its effect on structure, morphology, thermal‐ and pH‐responsive properties of the nanoparticles. It was found that CS‐PAA‐PNIPAAm nanoparticles could be well dispersed in the aqueous solution and carried positive charges on the surface. The addition of thermal‐sensitive NIPAAm monomer affected the polymerization mechanism and interactions between CS and AA. The particle size of the nanoparticles was found to be varied with the composition of NIPAAm monomer in the feed. The synthesized nanoparticles exhibited stimuli‐responsive properties, and their mean diameter thus could be manipulated by changing pH value and temperature of the environment. The nanoparticles showed a continuous release of the encapsulated doxycycline hyclate up to 10 days during an in vitro release experiment. The environmentally responsive nanoparticles are expected to be used in many fields such as drug delivery system. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2798–2810, 2009