Comparison of morphologies and mechanical properties of crosslinked epoxies modified by polystyrene and poly(methyl methacrylate)) or by the corresponding block copolymer polystyrene-b-poly(methyl methacrylate)

Polystyrene (PS, M_n=28,400, PI=1.07), poly(methyl methacrylate) (PMMA, M_n=88,600, PI=1.03), and PS (50,000)-b-PMMA (54,000) (PI=1.04), were used as modifiers of an epoxy formulation based on diglycidyl ether of bisphenol A (DGEBA) and m-xylylene diamine (MXDA). Both PS and PMMA were initially miscible in the stoichiometric mixture of DGEBA and MXDA at 80 °C, but were phase separated in the course of polymerization. Solutions containing 5 wt% of each one of both linear polymers exhibited a double phase separation. A PS-rich phase was segregated at a conversion close to 0.02 and a PMMA rich phase was phase separated at a conversion close to 0.2. Final morphologies, observed by scanning electron microscopy (SEM), consisted on a separate dispersion of PS and PMMA domains. A completely different morphology was observed when employing 10 wt% of PS-b-PMMA as modifier. PS blocks with M_n=50,000 were not soluble in the initial formulation. However, they were dispersed as micelles stabilized by the miscible PMMA blocks, leading to a transparent solution up to the conversion where PMMA blocks began to phase separate. A coalescence of the micellar structure into a continuous thermoplastic phase percolating the epoxy matrix was observed. The elastic modulus and yield stress of the cured blend modified by both PS and PMMA were 2.64 GPa and 97.2 MPa, respectively. For the blend modified by an equivalent amount of block copolymer these values were reduced to 2.14 GPa and 90.0 MPa. Therefore, using a block copolymer instead of the mixture of individual homopolymers and selecting an appropriate epoxy-amine formulation to provoke phase separation of the miscible block well before gelation, enables to transform a micellar structure into a bicontinuous thermoplastic/thermoset structure that exhibits the desired decrease in yield stress necessary for toughening purposes.     

Thermoresponsive core-shell-corona micelles of poly(ethyleneglycol)-b-poly(N-isopropylacrylamide)-b-polystyrene

Core-shell-corona micelles with a thermoresponsive shell self-assembled by triblock copolymer of poly(ethyleneglycol)-b-poly(N-isopropylacrylamide)-b-polystyrene (PEG₄₅-b-PNIPAM₁₆₈-b-PS₄₆) are studied by ¹H NMR, light scattering and atomic force microscopy. The thermoresponsive triblock copolymer, which has a relatively short hydrophobic PS block, can disperse in water at room temperature to form core-shell-corona micelles with the hydrophobic PS block as core, the thermoresponsive PNIPAM block as shell and the hydrophilic PEG block as corona. At temperature above lower critical solution temperature (LCST) of the PNIPAM block, the PNIPAM chains gradually collapse on the PS core to shrink the size and change the structure of the resultant core-shell-corona micelles with temperature increasing. It is found that there possibly exists an interface between the PNIPAM shell and PEG corona of the core-shell-corona micelles at temperature above LCST of the PNIPAM block.     

A new approach in the study of tethered diblock copolymer surface morphology and its tethering density dependence

A poly(l-lactic acid)-block-polystyrene-block-poly(methyl methacrylate) (PLLA-b-PS-b-PMMA) triblock copolymer was synthesized with a crystalline PLLA end block. Single crystals of this triblock copolymer grown in dilute solution could generate uniformly tethered diblock copolymer brushes, PS-b-PMMA, on the PLLA single crystal substrate. The diblock copolymer brushes exhibited responsive, characteristic surface structures after solvent treatment depending upon the quality of the solvent in relation to each block. The chemical compositions of these surface structures were detected via the surface enhanced Raman scattering technique. Using atomic force microscopy, the physical morphologies of these surface structures were identified as micelles in cyclohexane and “onion”-like morphologies in 2-methoxyethanol, especially when the PS-b-PMMA tethered chains were at low tethering density.     

Visualization of block copolymer distribution on a sheared drop

We have visualized a fluorescently-labeled poly(styrene-b-methylmethacrylate) (NBD-PS-b-PMMA) block copolymer on the surface of a polymethylmethacrylate (PMMA) drop in a polystyrene (PS) matrix. Confocal microscopy revealed that the block copolymer distributed uniformly on the drop surface before deformation. However, in shear flow the copolymer concentration was higher at the tips and edges of the drop. Visualization of drop deformation using a counter-rotating apparatus showed enhanced drop deformation for a drop with block copolymer resulting in larger area generation. Drops with block copolymer showed widening even for shear strains exceeding 10, in contrast to bare drops, which first widened and then shrank. These results agree qualitatively with the observed distribution of fluorescent block copolymer. Copolymer concentration is highest in the regions of high curvature, where lowering interfacial tension should be most effective in retarding drop retraction. Block copolymer on these highly curved surfaces is found to be very effective since the exact theory for zero interfacial tension by Cristini fits our drop widening results well.     

Reaction-induced microphase separation in thermosetting blends of epoxy resin with poly(methyl methacrylate)-block-polystyrene block copolymers: Effect of topologies of block copolymers on morphological structures

Polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) block copolymers with linear and tetra-armed star-shaped topological structures were synthesized via sequential atomic transfer radical polymerization (ATRP). With pentaerythritol tetrakis(2-bromoisobutyrate) as the initiator, the star-shaped block copolymers with two sequential structures (i.e., s-PMMA-b-PS and s-PS-b-PMMA) were prepared and the arm lengths and composition of the star-shaped block copolymers were controlled to be comparable with those of the linear PS-b-PMMA (denoted as l-PS-b-PMMA). The block copolymers were incorporated into epoxy resin to access the nanostructures in epoxy thermosets, by knowing that PMMA is miscible with epoxy after and before curing reaction whereas the reaction-induced phase separation occurred in the thermosetting blends of epoxy resin with PS. Considering the difference in miscibility of epoxy with PMMA and/or PS, it is judged that the reaction-induced microphase separation occurred in the systems. The design of these block copolymers allows one to investigate the effect of topological structures of block copolymers on the morphological structures of the thermosets. By means of atomic force microscopy (AFM) and small-angle X-ray scattering (SAXS), the morphology of the thermosets was examined. It is found that the nanostructures were formed in the thermosets containing l-PMMA-b-PS and s-PS-b-PMMA block copolymers. It is noted that the long-range order of the nanostructures in the epoxy thermosets containing l-PMMA-b-PS is obviously higher than that in the system containing s-PS-b-PMMA. However, the macroscopic phase separation occurred in the thermosetting blends of epoxy resin with s-PMMA-b-PS block copolymer.     

Sequence distribution affect the phase behavior and hydrogen bonding strength in blends of poly(vinylphenol-co-methyl methacrylate) with poly(ethylene oxide)

Experimental results indicate that the PEO was miscible with PVPh-r-PMMA copolymers as shown by the existence of single composition-dependent glass transition temperature over the entire compositions. However, the PVPh-b-PMMA copolymer with PEO shows a like closed loop phase-separated region in this copolymer/homopolymer blend system. Furthermore, FTIR reveals that at least three competing equilibrium are present in these blends; self-association (hydroxyl-hydroxyl), interassociation (hydroxyl-carbonyl) of PVPh-co-PMMA, and hydroxyl-ether interassociation between PVPh and PEO. Based on the Painter-Coleman Association Model (PCAM), a value for inter-association, K_C=300 is obtained in PVPh-b-PMMA/PEO blend system at room temperature. Although the relative ratio of interassociation equilibrium constant of PEO to PMMA is larger in PVPh-b-PMMA/PEO blend system, the PVPh-r-PMMA/PEO blend system has greater Δν and greater homogeneity at the molecular scale than the PVPh-b-PMMA/PEO blend system because of the ΔK effect.     

Morphology of polystyrene/polystyrene-block-poly(methyl methacrylate)/poly(methyl methacrylate) composite particles

Polystyrene/polystyrene-block-poly(methyl methacrylate)/poly(methyl methacrylate) (PS/PS-b-PMMA/PMMA) composite particles were prepared by releasing toluene from PS/PS-b-PMMA/PMMA/toluene droplets dispersed in a sodium dodecyl sulfate aqueous solution. The morphology of the composite particles was affected by release rate of toluene, the molecular weight of PS-b-PMMA, droplet size, and polymer composition. ‘Onion-like’ multilayered composite particles were prepared from toluene droplets of PS-b-PMMA and of PS/PS-b-PMMA/PMMA, in which the weights of PS and PMMA were the same. The layer thicknesses of the latter multilayered composite particles increased with an increase in the amount of the homopolymers. PS-b-PMMA/PS composite particles had a sea-islands structure, in which PMMA domains were dispersed in a PS matrix. On the other hand, PS-b-PMMA/PMMA composite particles had a cylinder-like structure consisting of a PMMA matrix and PS domains.     

Foaming behavior of isotactic polypropylene in supercritical CO2 influenced by phase morphology via chain grafting

Polystyrene (PS) and poly(methyl methacrylate) (PMMA) grafted isotactic polypropylene copolymers (iPP-g-PS and iPP-g-PMMA) with well-defined chain structure were synthesized by atom transfer radical polymerization using a branched iPP (iPP-B) as polymerization precursor. The branched and grafted iPP were foamed by using supercritical CO₂ as the blowing agent with a batch method. Compared to linear iPP foam, the iPP-B foams had well-defined close cell structure and increased cell density resulted from increased melt strength. Further incorporating PS and PMMA graft chains into iPP-B decreased the crystal size and increased the crystal density of grafted copolymers. In iPP-g-PS foaming, the enhanced heterogeneous nucleation by crystalline/amorphous interface further decreased the cell size, increased the cell density, and uniformized the cell size distribution. In contrast to this, the iPP-g-PMMA foams exhibited the poor cell morphology, i.e., large amount of unfoamed regions and just a few cells distributed among those unfoamed regions, although the crystal size and crystal density of iPP-g-PMMA were similar to those of iPP-g-PS. It was found that the iPP-g-PMMA exhibited PMMA-rich dispersed phase, which had higher CO₂ solubility and lower nucleation energy barrier than copolymer matrix did. The preferential cell nucleation within the PMMA-rich phase or at its interface with the matrix accounted for the poor cell morphology. The different effect of phase morphology on the foaming behavior of PS and PMMA grafted copolymers is discussed with the classical nucleation theory.     

Methacrylate/acrylate ABA triblock copolymers by atom transfer radical polymerization; their properties and application as a mediator for organically dispersible gold nanoparticles

This investigation reports the preparation of a series of well-defined Poly(methyl methacrylate)-b-poly(hexyl acrylate)-b-poly (methyl methacrylate) (PMMA-b-PHA-b-PMMA) triblock copolymers by Atom Transfer Radical Polymerization (ATRP). Their morphology, dynamic mechanical and tensile properties are thoroughly investigated. Phase separation is observed for all the above-mentioned triblock copolymers, which contain PMMA outer blocks in the molecular weight (M_n) range of 10,000-80,000 and PHA inner blocks with M_n in the range 20,000-40,000. The dynamic mechanical measurements essentially reveal two glass transitions and an intermediate flat rubbery plateau in between. Tensile studies indicate that as the PMMA content increases, there is an increase in tensile strength and decrease in elongation at break, which is the case for most of the thermoplastic elastomers (TPE). Eventually, the as prepared block copolymers (with PMMA content 50-80%) offer to be an effective stabilizer for preparing gold nanoparticle aggregates, the shape and size of which can be modulated by tuning the block copolymer composition. The formation of nanoparticle aggregates and their possible non-covalent interaction with the base polymer has been substantiated by UV-vis analysis, transmission electron microscopy, energy-dispersive X-ray spectroscopy, dynamic light scattering and Fourier transform infrared spectroscopy.     

Anomaly in SANS χ for polydisperse polystyrene-b-poly(isooctyl acrylate)

Small-angle neutron scattering (SANS) measurements have been performed on a disordered block copolymer from deuterated polystyrene (dPS) and self-adhesive poly(isooctyl acrylate) (POA) in order to elicit the effective Flory–Huggins χ, which carries the essence of the copolymer phase behavior. The copolymer sample for the measurement was prepared by blending two polydisperse dPS-b-POAs of different molecular weights, where the overall average size of the blend was low enough to ensure to be in the mean-field region but high enough to have discernible scattering intensities. The SANS profiles for the copolymer were fitted to Leibler's scattering function for a polydisperse copolymer system described by Schulz-Zimm distribution. The resultant χ as a function of inverse temperature was shown to have a strong entropic contribution and a weak enthalpic contribution. By adopting Sanchez-Balasz or ten Brinke-Karasz-type simple analysis for specific interactions, it was found that the entropically dominated χ for dPS-b-POA arises from the steric hindrance of long alkyl side groups of POA.     

Synthesis and characterization of poly(acrylonitrile-co-methylmethacrylate) nanocomposites reinforced by functionalized multiwalled carbon nanotubes

Polyacrylonitrile-co-poly(methylmethacrylate)/multiwalled carbon nanotubes (PAN-co-PMMA/MWCNTs) nanocomposites were synthesized by an in situ emulsifier-free polymerization method with variable percentages of functionalized carbon nanotube (f-MWCNT). MWCNTs were functionalized with concentrated H₂SO₄ and HNO₃ with a continuous sonication process. Chemical interaction of f-MWCNT with the copolymer was studied by UV-visible spectroscopy. Fourier transform infrared spectroscopy proved the interaction of f-MWCNT with the PAN-co-PMMA copolymer matrix. The structural interaction of f-MWCNT with copolymer matrix was investigated by X-ray diffraction study. The dispersion and morphology of the f-MWCNT in the copolymer matrix were studied by scanning electron microscopy and high-resolution transmission electron microscopy. It was noticed that the f-MWCNTs were uniformly dispersed within the copolymer matrix. The thermal property of the PAN-co-PMMA/f-MWCNT nanocomposite was analyzed by thermogravimetric analysis. It was noticed that the thermal stability of the PAN-co-PMMA/f-MWCNT nanocomposite was more than that of the virgin copolymer matrix. When the electrical conductivity property of the synthesized nanocomposite was measured, it was noticed that the better dispersion of f-MWCNT in the non-conductive PAN-co-PMMA copolymer matrix made the PAN-co-PMMA/f-MWCNT nanocomposites conductive. From the measurement of gas barrier properties of synthesized nanocomposites, it was assumed that the well-dispersed f-MWCNT in the copolymer matrix creates the huddles for penetration of oxygen gas. It was noticed that the oxygen permeability of the PAN-co-PMMA/f-MWCNT nanocomposite was reduced by five times as compared to that of the neat PAN-co-PMMA copolymer matrix. The PAN-co-PMMA/f-MWCNT nanocomposites with higher thermal stability and reduced oxygen permeability properties may be suitable for application as conducting packaging materials.     

Synthesis and self-assembly of a novel Y-shaped copolymer with a helical polypeptide arm

A novel biodegradable Y-shaped copolymer, poly(l-lactide)₂-b-poly(γ-benzyl-l-glutamic acid) (PLLA₂-b-PBLG), was synthesized by the ring-opening polymerization (ROP) of N-carboxyanhydride of γ-benzyl-l-glutamate (BLG-NCA) with centrally amino-functionalized poly(l-lactide), PLLA₂-NH₂, as a macroinitiator in a convenient way. The Y-shaped copolymer and its precursors were characterized by ¹H NMR, FT-IR, GPC, WAXD and DSC measurements. The self-assembly of the PLLA₂-b-PBLG copolymer in toluene and benzyl alcohol was examined. It was found that the self-assembly of the copolymer was dependent on solvent and on relative length of the PBLG block. For a copolymer with PLLA blocks of 26 in total degree of polymerization (DP), if the PBLG block was long enough (e.g., DP = 54 or more), the copolymer/toluene solution became a transparent gel at room temperature. In benzyl alcohol solution, only PLLA₂-b-PBLG containing ca. 190 BLG residues could form a gel; those with shorter PBLG blocks (e.g., DP = 54) became nano-scale fibrous aggregates and these aggregates were dispersed in benzyl alcohol homogeneously. Copolymers with short PBLG blocks behaved like a pure PLLA both in toluene and in benzyl alcohol. These experimental results were discussed and explained by virtue of the helical conformation of PBLG and the interactions between the solvents and the PLLA and/or PBLG segments.     

Dispersion of polymer-grafted magnetic nanoparticles in homopolymers and block copolymers

The dispersion of magnetic nanoparticles (NPs) in homopolymer poly(methyl methacrylate) (PMMA) and block copolymer poly(styrene-b-methyl methacrylate) (PS-b-PMMA) films is investigated by TEM and AFM. The magnetite (Fe₃O₄) NPs are grafted with PMMA brushes with molecular weights from M = 2.7 to 35.7 kg/mol. Whereas a uniform dispersion of NPs with the longest brush is obtained in a PMMA matrix (P = 37 and 77 kg/mol), NPs with shorter brushes are found to aggregate. This behavior is attributed to wet and dry brush theory, respectively. Upon mixing NPs with the shortest brush in PS-b-PMMA, as-cast and annealed films show a uniform dispersion at 1 wt%. However, at 10 wt%, PS-b-PMMA remains disordered upon annealing and the NPs aggregate into 22 nm domains, which is greater than the domain size of the PMMA lamellae, 18 nm. For the longest brush length, the NPs aggregate into domains that are much larger than the lamellae and are encapsulated by PS-b-PMMA which form an onion-ring morphology. Using a multi-component Flory-Huggins theory, the concentrations at which the NPs are expected to phase separate in solution are calculated and found to be in good agreement with experimental observations of aggregation.     

Synthesis, thermal properties, and specific interactions of high Tg increase in poly(2,6-dimethyl-1,4-phenylene oxide)-block-polystyrene copolymers

We have synthesized a series of block copolymers of poly(2,6-dimethyl-1,4-phenylene oxide) and polystyrene (PPO-b-PS copolymer) by atom transfer radical polymerization. The PS content in these copolymer systems was determined by using infrared spectroscopy, thermal gravimetric analysis, and solution and solid-state NMR spectroscopy; good correlations exist between these characterization methods. DSC analyses indicated that the PPO-b-PS copolymers have higher glass transition temperatures than do their corresponding PPO/PS blends. Our FTIR and solid-state NMR spectroscopic analyses suggest that the PPO-b-PS copolymers possess stronger specific interactions that are responsible for the observed relatively higher values of T_g. We found one single dynamic relaxation from the dynamic mechanical analysis, which implies dynamic homogeneity exists in the PPO-b-PS copolymer; this result is consistent with the one single proton spin-lattice relaxation time observed in the rotating frame [T_1ρ(H)] during solid state NMR spectroscopic analysis. In addition, the 2D FTIR spectroscopy reveals evidence for the stronger interactions between segments of PPO and PS through the formation of π-cation complexes.     

Baroplastic behavior of miscible block copolymer blends

Pressure dependence of various phase transitions for the miscible block copolymer (BCP) blends was evaluated by depolarized light scattering (DPLS) and small-angle neutron scattering (SANS) measurements, in which the blends consist of a polystyrene-b-poly(n-butyl methacrylate) (PS-b-PnBMA) and a deuterated polystyrene-b-poly(n-hexyl methacrylate) (dPS-b-PnHMA). Excellent baroplasticity was observed in nearly symmetric blends of PS-b-PnBMA/dPS-b-PnHMA, leading to the most outstanding pressure coefficients, |dT/dP|, in a closed-loop type phase behavior between a lower disorder-to-order transition (LDOT) and an order-to-disorder transition (ODT) type phase behavior. Together with the estimated pressure coefficients based on the values of enthalpic and volumetric changes at phase transitions, we demonstrate that the entropic compressibility for the miscible BCP blends is a baroplastic indicator, which was characterized by the negative volume change on mixing (ΔV_mix) at transitions.     

Complicated phase behavior and ionic conductivities of PVP-co-PMMA-based polymer electrolytes

We have used DSC, FTIR spectroscopy, and ac impedance techniques to investigate the interactions that occur within complexes of poly(vinylpyrrolidone-co-methyl methacrylate) (PVP-co-PMMA) and lithium perchlorate (LiClO₄) as well as these systems' phase behavior and ionic conductivities. The presence of MMA moieties in the PVP-co-PMMA random copolymer has an inert diluent effect that reduces the degree of self-association of the PVP molecules and causes a negative deviation in the glass transition temperature (T_g). In the binary LiClO₄/PVP blends, the presence of a small amount of LiClO₄ reduces the strong dipole-dipole interactions within PVP and leads to a lower T_g. Further addition of LiClO₄ increases T_g as a result of ion-dipole interactions between LiClO₄ and PVP. In LiClO₄/PVP-co-PMMA blend systems, for which the three individual systems—the PVP-co-PMMA copolymer and the LiClO₄/PVP and LiClO₄/PMMA blends—are miscible at all compositional ratios, a phase-separated loop exists at certain compositions due to a complicated series of interactions among the LiClO₄, PVP and PMMA units. The PMMA-rich component in the PVP-co-PMMA copolymer tends to be excluded, and this phenomenon results in phase separation. At a LiClO₄ content of 20 wt% salt, the maximum ionic conductivity occurred for a LiClO₄/VP57 blend (i.e., 57 mol% VP units in the PVP-co-PMMA copolymer).     

Swelling behavior of ordered miktoarm star block copolymer-homopolymer blends

We report the morphological characterization of asymmetric miktoarm star block copolymers of the (PS-b-PI)_nPS type where n=2,3 (denoted 2DB and 3DB miktoarm stars, respectively) and a symmetric super H-shaped block copolymer of the (PS-b-PI)₃PS(PI-b-PS)₃ type (denoted SH) which were synthesized by anionic polymerization. The initial volume fraction of PS (φ_PS) for each copolymer was 0.51-0.56, giving a lamellar morphology. Addition of homopolystyrene (hPS) with a molecular weight lower than the respective PS blocks in the neat materials lead to a transition from the lamellar structure to hexagonally packed cylinders. Addition of low molecular weight homopolyisoprene (hPI) on the other hand, only resulted in swollen lamellae even when the overall composition was highly asymmetric (80/20). Changes in the lamellar spacing as well as in the respective PS and PI layer thickness were measured by SAXS. The transition from lamellae to cylinders with increased PS content occurred without the observation of an intervening cubic morphology for the 2DB and 3DB miktoarm stars. However, blends with 30 and 35% hPS ((φ_PS)_total=0.68-0.70) with the super H-shaped block copolymer lead to the observation of lamellar-catenoid structures.     

Effects of substrate roughness on the orientation of cylindrical domains in thin films of a polystyrene-poly(methylmethacrylate) diblock copolymer studied using atomic force microscopy and cyclic voltammetry

This paper describes the orientation of cylindrical domains in thin films of a polystyrene-poly(methylmethacrylate) diblock copolymer (PS-b-PMMA; 0.3 as the PMMA volume fraction) on gold and oxide-coated Si substrates having different surface roughness. Atomic force microscopy images of PS-b-PMMA films having thickness similar to the domain periodicity permitted us to study the effects of substrate roughness and block affinity on domain orientation. PS-b-PMMA films on gold substrates showed metastable vertical domain orientation that was attained more slowly on rougher substrates. In contrast, the domains were horizontally oriented on oxide-coated Si regardless of surface roughness and the annealing conditions examined. In addition, cyclic voltammetry data for PS-b-PMMA films on gold substrates whose PMMA domains were etched suggested that the metastable vertically oriented domains reached the underlying substrates. These results indicate that PS-b-PMMA films containing vertically oriented cylindrical domains can be obtained by using rough gold substrates upon annealing under controlled conditions.     

Synthesis and characterization of well-defined hydrophilic block copolymer brushes by aqueous ATRP

Homopolymer brushes of poly(N,N-dimethylacrylamide) (PDMA), poly(methoxyethylacrylamide) (PMEA) and poly(N-isopropylacrylamide)(PNIPAM) grown on atom transfer radical polymerization (ATRP) initiator functionalized latex particles were used as macroinitiators for the synthesis of PDMA-b-PNIPAM/PMEA, PMEA-b-PDMA/PNIPAM and PNIPAM-b-PDMA block copolymer brushes by surface initiated aqueous ATRP. The grafted homopolymer and block copolymer brushes were analyzed for molecular weight, molecular weight distribution, chain grafting density, composition and hydrodynamic thickness (HT) using gel permeation chromatography-multi-angle laser light scattering, ¹H NMR, particle size analysis and atomic force microscopy (AFM) techniques. The measured graft molecular weight increased following the second ATRP reaction in all cases, indicating the second block had been added. Chain growth depended on the nature of the monomer used for block copolymerization and its concentration. Unimodal distribution of polymer chains in GPC with non-overlap of molar mass-elution volume curves implied an efficient block copolymerization. This was supported by the increase in HT measured by particle size analysis, equilibrium thickness observed by AFM and the composition of the block copolymer layer by ¹H NMR analysis, both in situ and on cleaved chains in solution. ¹H NMR analysis of the grafted latex and cleaved polymers from the surface demonstrated that accurate determination of the copolymer composition by this method is possible without detaching polymer chains from surface. Block copolymer brushes obey the same power law dependence of HT on molecular weight as homopolymer brushes in good solvent conditions. The NIPAM-containing block copolymer brushes were sensitive to changes in the environment as shown by a decrease in HT with increase in the temperature of the medium.