Effect of atom transfer radical polymerization macroinitiator on properties of poly(meth)acrylate-based pentablock type of thermoplastic elastomers

We report well controlled synthesis of novel tri-component [polyisobutylene (PIB), poly(n-butyl acrylate) (PnBA) and poly(methyl methacrylate) (PMMA)] pentablock copolymers (PMMA-b-PnBA-b-PIB-b-PnBA-b-PMMA) by Atom Transfer Radical Polymerization (ATRP) using PIB as a macroinitiator. The surface properties (hydrophobicity, in vitro oxidative stability and cellular interaction) and the bulk properties (phase separation and mechanical properties) of the PIB-containing pentablock copolymers were compared with PMMA-b-PnBA-b-PDMS-b-PnBA-b-PMMA (where PDMS = polydimethylsiloxane) and conventional PMMA-b-PnBA-b-PMMA copolymers synthesized by PDMS and PnBA macroinitiators respectively. It is revealed that type of ATRP macroinitiator (with low glass transition temperature) influences the properties of resultant pentablock copolymers in terms of phase separation, mechanical properties in vitro oxidative stability, cytocompatibility and cell proliferation. Pentablock copolymers synthesized by PIB macroinitiator exhibited superior overall properties compared to pentablock copolymers synthesized by PDMS macroinitiator and neat triblock copolymer synthesized by PnBA macroinitiator. Among the copolymers tested, one with composition PIB:PnBA:PMMA = 10:64:26 (w/w) exhibited best mechanical property, oxidative stability and cytocompatibility. The newly designed PIB-containing pentablock copolymer may be useful where softness, flexibility, processability and biostability/cytocompatibility are desired.     

Monomer casting nylon‐6‐b‐polyether amine copolymers: Synthesis and antistatic property

MC nylon‐6‐b‐polyether amine(PEA)copolymers were synthesized with macroinitiator based on amino‐terminated PEA functionalized with isocyanate via in situ polymerization. It was found that introduction of PEA delayed the polymerization process of caprolactam, resulting in the decrease of molecular weight of the copolymer. With increasing content of PEA, the melting peak started declining and widening, while the crystallinity and crystal grain size decreased, indicating weakening of the crystallization ability of nylon‐6 matrix. The fracture surfaces of the copolymer changed from irregular mosaic to the striation, presenting tough fracture characteristic, and the notched impact strength of the copolymers were improved dramatically. The electrical resistivity of the copolymers was increased by three orders of magnitude, and kept stable with prolonging storage time, indicating a permanently antistatic ability. The improved antistatic mechanism was deduced by the increase of concentration of oxygen atom and C? O group on the surface of the copolymers with increasing PEA content. The water contact angle decreased and surface tension increased, and finally the hydrophilicity of the copolymers was enhanced, resulting in the fairly good antistatic behavior of the copolymers by absorbing moisture from air. POLYM. ENG. SCI., 56:817–828, 2016. © 2016 Society of Plastics Engineers     

Preparation and characterization of block and graft copolymers using macroazoinitiators having siloxane units

α,ω-Amine terminated organofunctional polydimethylsiloxane (PDMS) was condensed with 4,4′-azobis-4-cyanopentanoyl chloride (ACPC) to prepare macroazoinitiators containing siloxane units. Interfacial polycondensation reaction at room temperature was applied: ACPC was slightly dissolved in carbon tetrachloride and it was poured on aqueous NaOH solution of PDMS. Block copolymers containing PDMS as a block segment combined with polystyrene (PS) have been derived by the polymerization of styrene monomer initiated by these macroazoinitiators. PS-b-PDMS block copolymers were characterized by using nuclear magnetic resonance and infrared spectroscopy. Thermal and mechanical properties of the block copolymers were studied by using thermogravimetric analysis, differential scanning calorimetry, and a Tensilon stress-strain instrument. The morphology of block copolymers was investigated by scanning electron microscopy. PDMS-g-polybutadiene (PBd) graft copolymers were also prepared by reaction of PBd with the above macroazo-initiator. Increase in the amount of macroazoinitiator in the mixture of PBd (52% w/w) leads to the formation of crosslinked graft copolymers. Molecular weights of soluble graft copolymer samples were between 450 and 600 K with a polydispersity of 2.0–2.3. © 1996 John Wiley & Sons, Inc.     

Synthesis and surface properties of polydimethylsiloxane‐based block copolymers: poly[dimethylsiloxane‐block‐ (ethyl methacrylate)] and poly[dimethylsiloxane‐block‐(hydroxyethyl methacrylate)]

A polydimethylsiloxane (PDMS) macroazoinitiator was synthesized from bis(hydroxyalkyl)‐terminated PDMS and 4,4′‐azobis‐4‐cyanopentanoic acid by a condensation reaction. The bifunctional macroinitiator was used for the block copolymerization of ethyl methacrylate (EMA) and 2‐(trimethylsilyloxy)ethyl methacrylate (TMSHEMA) monomers. The poly(DMS‐block‐EMA) and poly(DMS‐block‐TMSHEMA) copolymers thus obtained were characterized using Fourier transform infrared and ¹H NMR spectroscopy and differential scanning calorimetry. After the deprotection of trimethylsilyl groups, poly(DMS‐block‐HEMA) and poly(DMS‐block‐EMA) copolymer film surfaces were analysed using scanning electron microscopy and X‐ray photoelectron spectroscopy. The effects of the PDMS concentration in the copolymers on both air and glass sides of films were examined. The PDMS segments oriented and moved to the glass side in poly(DMS‐block‐EMA) copolymer film while orientation to the air side became evident with increasing DMS content in poly(DMS‐block‐HEMA) copolymer film. The block copolymerization technique described here is a versatile and economic method and is also applicable to a wide range of monomers. The copolymers obtained have phase‐separated morphologies and the effects of DMS segments on copolymer film surfaces are different at the glass and air sides. Copyright © 2010 Society of Chemical Industry     

Surface microphase separation in PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films

Well‐defined poly(dimethylsiloxane)‐block‐poly(methyl methacrylate)‐block‐poly(2,2,3,3,4,4,4‐heptafluorobutyl methacrylate) (PDMS‐b‐PMMA‐b‐PHFBMA) triblock copolymers were synthesized via atom transfer radical polymerization (ATRP). Surface microphase separation in the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films was investigated. The microstructure of the block copolymers was investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). Surface composition was studied by X‐ray photoelectron spectroscopy (XPS). The chemical composition at the surface was determined by the surface microphase separation in the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films. The increase of the PHFBMA content could strengthen the microphase separation behavior in the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymer films and reduce their surface tension. Comparison between the PDMS‐b‐PMMA‐b‐PHFBMA triblock copolymers and the PDMS‐b‐PHFBMA diblock copolymers showed that the introduction of the PMMA segments promote the fluorine segregation onto the surface and decrease the fluorine content in the copolymers with low surface energy. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A new macroinitiator for the synthesis of triblock copolymers PA12‐b‐PDMS‐b‐PA12

A new PDMS macroinitiator is proposed for the anionic ring‐opening polymerization of lactams. This α,ω‐dicarbamoyloxy caprolactam PDMS macroinitiator was readily obtained in quantitative yield, by an original synthesis scheme in two steps, which involved the scarcely reported reaction of isocyanates with silanol groups. It was then shown that this bifunctional macroinitiator enabled to synthesize triblock copolymers PA12‐b‐PDMS‐b‐PA12 by polymerization of lauryl lactam (LL) at high temperature (200°C) in inert atmosphere under conditions compatible with reactive extrusion processes. Another related high molar weight α,ω‐diacyllactam PDMS macroinitiator was also successfully used in the polymerization of LL under the same conditions, therefore overcoming the limitations formerly reported for this type of macroinitiators during the polymerization ε‐caprolactam (ε‐CL) at a much lower temperature (80°C). Triblock copolymers with a wide range of PA12 /molar weights (M_n: ～ 10,800–250,000 Da) were eventually obtained by using both types of macroinitiators. DMTA and DSC analyses showed that their thermal properties were strongly dependent upon their respective contents in soft and hard blocks. Such triblock copolymers already appear very promising for the highly effective in situ compatibilization of PA12/PDMS blends as shown by recent complementary results obtained in our laboratory. © 2006 Wiley Periodicals, Inc. J Appl PolymSci 102: 2818–2831, 2006     

Microscopic surface and bulk morphology of semicrystalline poly(dimethylsiloxane)–polyester copolymers

In this study, two series of semicrystalline poly(dimethylsiloxane) (PDMS)–polyester segmented copolymers with various PDMS contents were synthesized. One series was based on polybutylene adipate (PBA) as the polyester segment and the other was based on a polybutylene cyclohexanedicarboxylate ester (PBCH) segment. The copolymers were characterized using ¹H‐nuclear magnetic resonance, size exclusion chromatography, dynamic mechanical analyses, differential scanning calorimetry (DSC), and wide‐angle X‐ray diffraction (WAXD). The microscopic surface morphology and the microscopic bulk morphology were investigated using atomic force microscopy (AFM) and transmission electron microscopy, respectively. The effects of the polyester type and the PDMS content on the crystallinity degree as well as the copolymer surface and bulk morphology at room temperature were investigated for each series. DSC and WAXD results showed the ability of the copolymers to crystallize, to various degrees, depending on the polyester type and the PDMS content. The results showed that the PDMS content had a greater influence on the crystallinity degree in the PDMS‐s‐PBCH (cycloaliphatic) copolymer series than in the PDMS‐s‐PBA (aliphatic) copolymer series. In the copolymers with a low PDMS content, the AFM images showed spherulitic crystal morphology and evidence of PDMS nanodomains in between the crystal lamellae of the ester phase on the copolymer surface. A heterogeneous distribution of the PDMS domains was also observed for these copolymers in the bulk morphology as a result of this segregation between the polyester lamellae. All the copolymers, in both series, showed microphase separation as a result of the incompatibility between the PDMS segment and the polyester segment. Three types of surfaces and bulk morphologies were observed: spherical microdomains of PDMS in a matrix of polyester, bicontinuous double‐diamond type morphology, and spherical microdomains of polyester in a matrix of PDMS as the PDMS content increases. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis and properties of triblock copolymers containing PDMS via AGET ATRP

The bromo-terminated macroinitiator was prepared by direct addition reaction of difunctional poly(dimethylsiloxane) (PDMS) containing methyl methacrylate end groups with hydrobromic acid in acetic acid under mild conditions, and well-defined triblock copolymers of poly(methyl methacrylate-b-dimethylsiloxane-b-methyl methacrylate) (MMA-b-DMS-b-MMA) were synthesized via activators generated by election transfer atom transfer radical polymerization (AGET ATRP). The gel permeation chromatography data obtained verified the polymerization and showed the well controlling of the reaction. FTIR and ¹H NMR measured the structure of the macroinitiator and copolymers. The contact angle measurement indicated that the water contact angles decreased gradually with the increasing of PMMA block content. The self-assembly behaviors of the triblock polymer were studied by transmission electron micrograph, scanning electron microscopy, and dynamic light scattering measurement. The results indicated that the polymers could self-assemble into various complex morphologies in different solvents and the morphologies depended on the properties of solvents. The possible molecular packing models for self-assembly behaviors of the ABA triblock polymers were proposed.     

Poly(dimethylsiloxane)urethane‐co‐poly(methyl methacrylate) with 2,4‐toluene diisocyanate and m‐xylene diisocyanate. I. Compatibility and impact strength of copolymers

In this study, slightly crosslinked poly(dimethylsiloxane)urethane‐co‐poly(methyl methacrylate) (PDMS urethane‐co‐PMMA) graft copolymers based on two diisocyanates, 2,4‐toluene diisocyanate (2,4‐TDI) and m‐xylene diisocyanate (m‐XDI), were successfully synthesized. Glass‐transition behaviors of the copolymers were investigated. Results confirm that PDMS–urethane and PMMA are miscible in the 2,4‐TDI system, but are only partially miscible in the m‐XDI system. The methylene groups adjoining the isocyanate in the m‐XDI system show increased phase‐separation behavior over the 2,4‐TDI system, in which the benzene ring adjoins the isocyanate. The functional group of PDMS–urethane improves the impact strength of the copolymers. The toughness depends on the compatibility of PDMS–urethane and PMMA segments in the copolymers. In the m‐XDI system, the impact strength of the copolymer containing 3.75 phr macromonomer achieves a maximum value (from 13.02 to 22.21 J/m). The fracture behavior and impact strength of the copolymers in the 2,4‐TDI system are similar to that of PMMA homopolymer, although they are independent of the macromonomer content in the copolymer. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1875–1885, 2002     

Polydimethylsiloxane/monomer casting nylon copolymers: Preparation,flame-retardant properties,and wear-resistant properties

In order to improve the toughness, wear resistance, and combustion properties of the monomer casting nylon (MC nylon) materials, the polydimethylsiloxane (PDMS) segment is bonded to the nylon molecular chain by copolymerization. PDMS/MC nylon copolymers are prepared via in situ anionic polymerization with macro-activator based on PDMS terminated with hexamethylene diisocyanate. The effects of different macro-activator content on the mechanical properties, water absorption, thermal stability, friction and wear properties, and combustion properties of the copolymers are characterized. The results show that the impact strength of the copolymer improves significantly (optimally increases by 2.6 times) and the water absorption rate decreases with the increase of PDMS content. The introduction of the silicon–oxygen structure reduces the peak heat release rate of copolymer materials (optimally decreases about 28.7%), while it promotes the decomposition of the system, resulting in a slight decrease in the thermal stability of the materials. Adding 5 wt % PDMS can decrease the wear loss of MC nylon from 6.2 mg of pure nylon to 1.6 mg. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48753.     

Synthesis and characterization of five-block copolymers prepared by vinyl pyrrolidinone and a macro initiator with poly(dimethylsiloxane) and polycaprolactone

A new generation of a series of five-block copolymers of poly(dimethylsiloxane) (PDMS), polycaprolactone (PCL), and polyvinyl pyrrolidinone (PVP), (PVP-PCL-PDMS-PCL-PVP), are synthesized to obtain new polymeric systems containing PDMS with improved compatibilities. For this, a commercial reactive triblock copolymer of PCL and PDMS, namely (PCL-PMDS-PCL), was used as the starting material from which the peroxidic macroinitiator was prepared. By use of physicochemical methods, a five-block copolymer structure was confirmed, and its characterization was accomplished. Mechanical and thermal test results showed higher thermal resistances and increased toughness characteristics of the copolymer as compared with that of the component homopolymers. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 1961–1969, 1997     

Studies on the curing behavior,thermal, and mechanical properties of epoxy resin-co-amine-functionalized lead phthalocyanine

A high performance copolymer was prepared by using epoxy (EP) resin as matrix and 3,10,17,24-tetra-aminoethoxy lead phthalocyanine (APbPc) as additive with dicyandiamide as curing agent. Fourier-transform infrared spectroscopy, dynamic mechanical analysis (DMA), differential scanning calorimetric analysis (DSC), and thermogravimetric analysis (TGA) were used to study the curing behavior, curing kinetics, dynamic mechanical properties, impact and tensile strength, and thermal stability of EP/APbPc blends. The experimental results show that APbPc, as a synergistic curing agent, can effectively reduce the curing temperature of epoxy resin. The curing kinetics of the copolymer was investigated by non-isothermal DSC to determine kinetic data and measurement of the activation energy. DMA, impact, and tensile strength tests proved that phthalocyanine can significantly improve the toughness and stiffness of epoxy resin. Highest values were seen on the 20 wt% loading of APbPc in the copolymers, energy storage modulus, and impact strength increased respectively 388.46 MPa and 3.6 kJ/m², T_g decreased 19.46°C. TGA curves indicated that the cured copolymers also exhibit excellent thermal properties.     

Synthesis and characterization of the feed ratio of polyethylene oxide (0 ∼ 10 wt % PEO) in the nylon‐6/PEO copolymer system

In this work, we have synthesis nylon‐6/polyethylene oxide (PEO) copolymer system based on feed ratio of PEO (0～ 10 wt %) through condensation polymerization in a pilot scale. The structure of copolymer was confirmed by Fourier transform infrared (FTIR) spectroscopy and verified by ¹H nuclear magnetic resonance (¹HNMR). The thermal properties were investigated by differential scanning calorimetry (DSC) and indicated both melting temperature (T_m) and cold crystallization temperature (T_c) appearing unapparent decreased while increased PEO content in copolymers. The incorporation of PEO into the nylon‐6 chain reduced its tensile strength, modulus, and heat distortion temperature (HDT). The notched Izod impact strength of and ductility of the copolymers improved significantly as the PEO content was increased. The plasticizing effect was caused by the soft segments from PEO, which increases the mobility of the molecular chain in the copolymers. The results of mechanical tests agree closely with dynamic mechanical analysis (DMA) measurements. A rheological investigation revealed that neat nylon‐6 and its copolymer displayed similar behavior. The crystalline structure was examined by wide‐angle X‐ray diffraction (WAXD). The results demonstrate that the addition of a little PEO altered the crystallization from the α form to the γ form, mainly owing to the breaking parts of the original H‐bonds by the incorporation of ether groups. A mechanism of interaction between the amide and the ether group in nylon‐6/PEO copolymers is proposed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis and characterization of styrene–N-butyl maleimide copolymers using iniferters containing thiyl end groups

The radical homopolymerization of styrene or copolymerization of styrene (S) with N-butyl maleimide (I) initiated by tetraethylthiuram disulfide was used to prepare macroinitiators having thiyl end groups. The S–I copolymers from the feeds containing 30–70 mol % I showed approximately alternating composition. The rate of copolymerization and molecular weights decreased with increasing maleimide derivative concentration in the feed; homopolymerization of I alone did not proceed. The macroinitiators served for synthesis of further S–I copolymers. Using polystyrene macroinitiator and the S–I copolymer with thiyl end groups in the polymerization of S–I mixture and styrene, respectively, the copolymers containing blocks of both polystyrene and alternating S–I copolymer were obtained. The copolymerization of S–I mixture initiated with the S–I copolymer bearing thiyl end groups led to the extension of macroinitiator chains by the blocks of alternating copolymer. The presence of the blocks in the polymer products was corroborated using elemental analysis, size exclusion chromatography, and differential scanning calorimetry. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67: 755–762, 1998     

Preparation and evaluation of hydrophobic surfaces of polyacrylate-polydimethylsiloxane copolymers for anti-icing

Two series of polyacrylate-polydimethylsiloxane (PDMS) copolymers, namely, polyacrylate-b-PDMS and polyacrylate-g-PDMS with three different molecular weights of PDMS blocks or side chains, were synthesized for formation of hydrophobic surfaces for anti-icing. The main purpose of this paper was to investigate the relationship between ice adhesion strength and the surface structure of the copolymers, and to find out how the prepared PDMS-containing polyacrylate copolymers are potentially used for anti-icing. The microphase-separated structure and the surface chemical composition were analyzed by transmission electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy, and ice adhesion strength was measured using a universal testing machine in a pull off mode. Results suggested that microphase separation appeared clearly in all the copolymers, especially for the block ones. The PDMS chains aggregated on the top of the polymer surfaces caused by microphase separation could weaken the interaction between the polymer surface and water, mainly hydrogen bond, which was demonstrated because of decrease of water contact angle hysteresis. Then, ice adhesion strength was decreased by the contribution of PDMS in the block copolymers or the graft copolymer with longer PDMS side chains. It is suggested that the polyacrylate-b-PDMS or polyacrylate-g-PDMS copolymers would have practical applications in preparation of anti-icing coatings.     

Synthesis of a polydimethylsiloxane-block-hydroxyl grafted acrylate prepolymer copolymer to improve the adhesion between silicone rubber and polyurethane by induced surface reconstruction

A new class of hydroxyl-functionalized polydimethylsiloxane-block-hydroxyl graft acrylate prepolymer (PDMS-b-HGAP) copolymers was synthesized. The copolymers were characterized using Fourier transform infrared spectroscopy as well as ¹H and ¹³C nuclear magnetic resonance spectroscopy. The hydroxyl groups of the HGAP were reacted with the chlorine terminal in the PDMS to yield a triblock copolymer consisting of two segments of PDMS linked to a HGAP segment. The induced surface reconstruction of silicone rubber (SR)by blending polysiloxane reactants with bifunctional PDMS-b-HGAP copolymers and curing using mold materials having high critical surface tension such as polyethyleneterephthalate was attempted to improve the adhesion between chemically-inert SR and polyurethane (PU). Surface characterization using Foruier transform infrared-attenuated total reflectance indicated that the surface of the SR was enriched with HGAP. The increased content of surface HGAP was suggested to account for the improved adhesion between SR and PU.     

Atom transfer radical polymerization of styrene and methyl (meth)acrylates initiated with poly(dimethylsiloxane) macroinitiator: Synthesis and characterization of triblock copolymers

Poly(dimethylsiloxane)(PDMS)‐based triblock copolymers were successfully synthesized via atom transfer radical polymerization (ATRP) initiated with bis(bromoalkyl)‐terminated PDMS macroinitiator (Br‐PDMS‐Br). First, Br‐PDMS‐Br was prepared by reaction between the bis(hydroxyalkyl)‐terminated PDMS and 2‐bromo‐2‐methylpropionyl bromide. PSt‐b‐PDMS‐b‐PSt, PMMA‐b‐PDMS‐b‐PMMA and PMA‐b‐PDMS‐b‐PMA triblock copolymers were then synthesized via ATRP of styrene (St), methyl methacrylate (MMA) and methyl acrylate (MA), respectively, in the presence of Br‐PDMS‐Br as a macroinitiator and CuCl/PMDETA as a catalyst system at 80 ^oC. Triblock copolymers were characterized by FTIR, ¹H‐NMR and GPC techniques. GPC results showed linear dependence of the number‐average molecular weight on the conversion as well as the narrow polydispersity indicies (PDI < 1.57) for the synthesized triblock copolymers which was lower than that of Br‐PDMS‐Br macroinitiator (PDI = 1.90), indicating the living/controlled characteristic of the reaction. Also, there was a very good agreement between the number‐average molecular weight calculated from ¹HNMR spectra and that calculated theoretically. Results showed that resulting copolymers have two glass transition temperatures, indicating that triblock copolymers have microphase separated morphology. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis, characterization and properties of chitosan modified with poly(ethylene glycol)-polydimethylsiloxane amphiphilic block copolymers

Synthesis of poly(ethylene glycol)-polydimethylsiloxane amphiphilic block copolymers is discussed herein. Siloxane prepolymer was first prepared via acid-catalyzed ring-opening polymerization of octamethylcyclotetrasiloxane (D₄) to form polydimethylsiloxane (PDMS) prepolymers. It was subsequently functionalized with hydroxy functional groups at both terminals. The hydroxy-terminated PDMS can readily react with acid-terminated poly(ethylene glycol) (PEG diacid) to give PEG-PDMS block copolymers without using any solvent. The PEG diacid was prepared from hydroxy-terminated PEG through the ring-opening reaction of succinic anhydride. Their chemical structures and molecular weights were characterized using ¹H NMR, FTIR and GPC, and thermal properties were determined by DSC. The PEG-PDMS copolymer was incorporated into chitosan in order that PDMS provided surface modification and PEG provided good water swelling properties to chitosan. Critical surface energy and swelling behavior of the modified chitosan as a function of the copolymer compositions and contents were investigated.     

Synthesis of well‐defined comb‐like amphiphilic copolymers with protonizable units in the pendent chains: 2. Poly(2‐(dimethylamino)ethyl methacrylate) grafted poly(methyl methacrylate‐co‐2‐hydroxyethyl methacrylate) copolymers and their association behavior in aqueous solution

Narrow‐distribution, well‐defined comb‐like amphiphilic copolymers are reported in this work. The copolymers are composed of poly(methyl methacrylate‐co‐2‐hydroxyethyl methacrylate) (P(MMA‐co‐HEMA)) as the backbones and poly(2‐(dimethylamino)ethyl methacrylate) (PDMAEMA) as the grafted chains, with the copolymer backbones being synthesized via atom‐transfer radical polymerization (ATRP) and the grafted chains by oxyanionic polymerization. The copolymers were characterized by gel permeation chromatography (GPC), Fourier‐transform infrared (FT‐IR) spectroscopy and ¹H NMR spectroscopy. The aggregation behavior in aqueous solutions of the comb‐like amphiphilic copolymers was also investigated. ¹H NMR spectroscopic and surface tension measurements all indicated that the copolymers could form micelles in aqueous solutions and they possessed high surface activity. The results of dynamic light scattering (DLS) and scanning electron microscopy (SEM) investigations showed that the hydrodynamic diameters of the comb‐like amphiphilic copolymer aggregates increased with dilution. Because of the protonizable properties of the graft chains, the surface activity properties and micellar state can be easily modulated by variations in pH. Copyright © 2004 Society of Chemical Industry     

Block copolymers derived from azobiscyanopentanoic acid. XI. Properties of silicone–PMMA block copolymers prepared via polysiloxane(azobiscyanopentanamide)s

Mechanical, thermal, and surface properties of poly(dimethylsiloxane)–poly(methyl methacrylate) block copolymers (PDMS-b-PMMA) prepared by the use of polysiloxane(azobiscyanopentanamide)s were intensively investigated. The mechanical strength of block copolymers was found to decrease with an increase of siloxane contents. Dynamic mechanical analysis (DMA) of block copolymers having long siloxane chain length (SCL) and high siloxane content revealed the existence of two glass transitions attributable to microphase separation of two segments. Differential scanning calorimetry (DSC) also gave some evidence of microphase separation supporting the DMA results. It was observed that the incorporation of PDMS segments in block copolymers improved thermal stability of PMMA, as confirmed by thermogravimetric analysis. Surface analysis of the block copolymers films cast from several solutions indicated surface accumulation of PDMS segments, as revealed by water contact angle and ESCA measurements.