Film formation of nano‐sized hard latex (PS) in soft polymer matrix (PBA): An excimer study

This work reports steady state fluorescence (SSF) technique for studying film formation from pyrene (P)‐labeled nano‐sized polystyrene (PS) and poly(n‐butyl acrylate) (PBA) hard/soft latex blends. Blend films were prepared from mixtures of PS and PBA in dispersion. Eight different blend films were prepared in various hard/soft latex compositions at room temperature and annealed at elevated temperatures above glass transition temperature (T_g) of polystyerene. Monomer (I_P) and excimer (I_E) intensities from P was measured after each annealing step to monitor the stages of film formation. The evolution of transparency of latex films was monitored using photon transmission intensity, I_tr. Film morphologies were examined by atomic force microscopy (AFM). The results showed that as the amount of hard component (PS) in the blend is decreased, a significant change occurred in both I_E/I_P and I_tr curves at a certain critical weight fraction (50 wt%) of PS hard latex. Two distinct film formation stages, which are named as void closure and interdiffusion were seen in (I_E/I_P) data above this fraction. However, below 50 wt% PS no film formation was observed. AFM pictures also confirmed these findings. Void closure and interdiffusion stages for (50–100) wt% range of PS were modeled and related activation energies were determined. There was no observable change in activation energies confirming that film formation behavior is not affected by varying the blend composition in this range. POLYM. COMPOS., 31:1611–1619, 2010. © 2009 Society of Plastics Engineers     

The effect of clay particles on film formation from polystyrene latex

Film formation from surfactant‐free polystyrene (PS) latex was performed in the presence of 5% Na‐montmorillonite (NaMMT). The composite films were prepared from pyrene (P)‐labeled PS particles at room temperature and annealed at elevated temperatures above the glass‐transition (T_g) temperature of polystyrene. Scattered light (I_s) and fluorescence intensity (I_P) from P were measured after each annealing step to monitor the stages of composite film formation. Minimum film formation temperature, T₀, and healing temperatures, T_h, were determined. Void closure and interdiffusion stages were modeled and related activation energies were measured. From these results, it was found that the presence of NaMMT in the PS latex film only affects the minimum film formation, but does not affect the void closure and backbone motion activities. POLYM. COMPOS., 27:299–308, 2006. © 2006 Society of Plastics Engineers     

Film formation from surfactant-free,slightly crosslinked,fluorescein-labeled polystyrene particles

A steady state-fluorescence (SSF) technique for studying film formation from surfactant-free, slightly crosslinked polystyrene (PS) latex particles is reported. The powder films were prepared from fluorescein (F)-labeled PS particles at room temperature. The mechanically strong films were obtained by annealing these films at elevated temperatures in 5, 10, 20, and 30 min time intervals above the glass transition (T_g) temperature of polystyrene. Scattered light (I_s) and fluorescence (I_F) intensities from F were monitored after each annealing step to investigate the three different film formation stages called void closure, healing, and interdiffusion. The evolution of transparency of the latex films was monitored by using a photon transmission technique. Scanning electron microscopy (SEM) was employed to detect the variation in physical structure of the annealed latex films. Onset temperature for void closure, T_m’, and healing temperatures, T_h, were determined and corresponding activation energies were measured. Void closure and interdiffusion stages were also modeled and the related activation energies were also determined. It was observed that lower energy is needed for the void closure process than interdiffusion of chains across the particle-particle boundaries.     

Films formed from polystyrene latex/clay composites: A fluorescence study

This study reports a steady-state fluorescence (SSF) technique for studying film formation from surfactant-free polystyrene (PS) latex and Na-montmorillonite (SNaM) composites. The composite films were prepared from pyrene (P)-labeled PS particles and SNaM clay at room temperature and annealed at elevated temperatures in 10-min intervals above glass transition temperature (t₃) of polystyrene. During the annealing processes, the transparency of the film improved considerably. Scattered light (I_s) and fluorescence intensity (I_p) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of composite films was monitored by using photon transmission intensity, I_tr. Scanning electron microscopy (SEM) was used to detect the variation in physical structure of annealed composite films. Minimum film formation temperature, T_q, and healing temperatures, T_h, were determined. Void closure and interdiffusion stages were modeled and related activation energies were determined. It was observed that both activation energies increased as the percent of SNaM was increased in composite films.     

Fluorescence study on Al2O3‐polystyrene latex composite film formation

This work reports a steady state fluorescence (SSF) technique for studying film formation from mixture of Al₂O₃ and polystyrene (PS) latex particles. The composite films were prepared from dispersion of pyrene (P)‐labeled PS particles in Al₂O₃ solution at room temperature and annealed at elevated temperatures in 10‐min time interval above glass transition (T_g) temperature of polystyrene. Nine different composites film were studied in various latex contents. Fluorescence intensities (I_P) from P were measured after each annealing step to monitor the stages of film formation. No variations in I_P were detected for the films prepared with higher than 33 wt% Al₂O₃ content. However films prepared below 33 wt% Al₂O₃ content show considerable increase in I_P above the certain onset temperature called minimum film forming temperature, T₀. Healing temperatures T_h, were determined from the maxima of I_P. Void closure and interdiffusion stages were modeled and related activation energies were determined and found to be 20 and 97 kJ.mol^–1, respectively. POLYM. COMPOS., 26:352–360, 2005. © 2005 Society of Plastics Engineers     

Film formation from polystyrene–poly(butyl acrylate‐co‐methyl methacrylate) latex blends

We have employed steady sate fluorescence (SSF) and UV‐visible (UVV) techniques to determine the film formation behavior of latex blends. Blend films were prepared from mixtures of a high‐T_g pyrene (P) labeled polystyrene (PS) latex and a low‐T_g copolymer of poly(butyl acrylate‐co‐methyl methacrylate) (BuA/MMA4). Eleven different blend films were prepared in various hard/soft latex compositions at room temperature and annealed at elevated temperatures above glass‐transition (T_g) temperature of polystyerene for 10 min. Fluorescence intensity (I_P) from P was measured after each annealing step to monitor the stages of film formation. The evolution of transparency of latex films was monitored using photon transmission intensity, I_tr. Film morphologies were examined by atomic force microscopy (AFM). A significant change occurs in both I_P and I_tr intensities at a certain critical weight fraction of hard latex (R_c = 0.3). Above R_c, two distinct film formation stages, which are named as void closure and interdiffusion processes, were seen in fluorescence data. Transparency of the films was decreased with decreasing PS content, indicating that a phase separation process occurs between PS and BuA/MMA4 phases by thermal treatment, which results in turbid films. However, below R_c, no change was observed in I_P and I_tr upon annealing, whereas transparency increased overall with increasing BuA/MMA4 ratio. We explained this result as the phase separation process between PS and BuA/MMA4 blends. These results were also confirmed by AFM pictures. Film formation stages above R_c were modeled and related activation energies were calculated. POLYM. COMPOS., 27:431–442, 2006. © 2006 Society of Plastics Engineers     

Film formation from nano‐sized polystrene latex covered with various TiO2 layers

Steady‐state fluorescence technique was used for studying film formation from TiO₂ covered nano‐sized polystyrene latex particles. The composite films were prepared from pyrene (P)‐labeled PS particles by covering them with various layers of TiO₂ at room temperature. These films then annealed at elevated temperatures in 10 min time interval above glass transition (T_g) temperature of polystyrene. Five different composite films were studied in various TiO₂ layer contents. Fluorescence emission intensity, I_P from P was measured after each annealing step to monitor the stages of film formation. Films present significant increase in I_P above the certain onset temperature called minimum film forming temperature, T₀. However, at higher annealing temperatures, I_P showed a decrease. Increase and decrease in I_P were modeled by void closure and interdiffusion processes and related activation energies were determined, respectively. Dissolution of annealed PS film, with high TiO₂ content presented a nice, ordered nano‐sized ceramic structure, which may predict the construction of nano‐layer photonic crystals. POLYM. COMPOS., 27:651–659, 2006. © 2006 Society of Plastics Engineers     

Particle size effect on the film‐forming process of PS/PBA composite latexes

In this work, the effect of hard particle size and blend ratio on the film formation behavior of hard polystyrene (PS) and soft poly(n‐butyl acrylate) (PBA) latex blends was studied by means of steady‐state fluorescence and UV–visible techniques in conjunction with atomic force microscopy. Three different sets of latexes were synthesized: PBA latex (diameter 97 nm), pyrene (P)‐labeled large PS (LgPS; diameter 900 nm), and small PS (SmPS; diameter 320 nm). Two different series of latex blends (LgPS/PBA and SmPS/PBA) were prepared with varying blend composition at room temperature separately. Films were then annealed at elevated temperatures above glass transition (T_g) temperature of PS. Fluorescence intensity (I_P) from P and photon transmission intensity (I_tr) were measured after each annealing step to monitor the stages of film formation. The results showed that a significant change occurred in I_P and I_tr at a certain critical weight fraction (R_c) of PBA. Below R_c, two distinct film formation stages, which are named as void closure and interdiffusion, were seen. However, at PBA concentrations nearer to or above R_c, no film formation can be achieved. Comparing to the LgPS/PBA, the sintering process of SmPS/PBA particles occurred at much lower temperatures. Film formation stages for R < R_c were modeled, and related activation energies were calculated. Void closure (ΔH) and interdiffusion (ΔE) activation energies for SmPS/PBA were also found smaller in comparing with LgPS/PBA series. However, ΔH and ΔE values were not changed much with the blend composition for both series. POLYM. COMPOS., 31:1637–1652, 2010. © 2009 Society of Plastics Engineers     

How the infrared radiation affects the film formation process from latexes?

In this study, the effect of the infrared radiative heating (IRH) was investigated on the film formation from composites of polystyrene (PS) latex particles and poly vinyl alcohol (PVA). The films were prepared as a pure PS and a mixture of PS and PVA particles at equal compositions at room temperature and they were annealed at elevated temperatures above the glass transition temperature (T_g) of PS for 10 min by using IRH technique. Identical experiments were performed by using standard convectional heating technique in oven as comparison. It was shown that the activation energy for the film formation from PS latex particles decreased considerably in IRH annealing technique. Photon transmission (PT) and steady state fluorescence (SSF) techniques were used to monitor the film formation process at each sintering step. Minimum film formation temperature, T_o, and healing temperature, T_h, were determined by the data obtained from the SSF and the PT measurements for each heating processes. The film formation was modeled as a void closure and as an interdiffusion stage below and above T_h, respectively. Scanning electron microscopy (SEM) was used to examine the variation in morphological structure of annealed composite films. It was observed that IRH heating causes more homogenous and more flat film surface than films annealed in the oven. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43289.     

Effects of aging on latex film formation from polystrene particles: A photon transmission study

Aging due to the storage time on latex film formation was studied using the photon transmission method. The UV visible technique was used to monitor the evolution of transparency during film formation from two different polystyrene (PS) particles produced by using two different steric stabilizers, i.e., polyvinyl alcohol and polyvinyl pyrrolidone. The latex films were prepared from PS particles at room temperature before and after aging and annealed at elevated temperatures in various time intervals above glass transition (T_g). The increase in the transmitted photon intensity I_tr was attributed to the increase in the number of disappeared particle–particle interfaces. Relative decrease in transparency and delay in film formation were observed in the aged latex films compared to the nonaged ones. The Prager–Tirrell model was employed to interpret the increase in crossing density at the junction surface. The back and forth activation energies (ΔE) were measured and found to be dependent on aging for a diffusing polymer chain across the junction surface. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2014–2021, 2001     

Photon transmission method for studying film formation from polstyrene latexes with different molecular weights

A photon‐transmission method was used to probe the evolution of transparency during film formation from polystyrene (PS) particles with different molecular weights. The latex films were formed at room temperature from the PS particles having two different average molecular weights and annealed at elevated temperatures in various time intervals above the glass transition (T_g). Onset temperatures (T_H) at given times (τ_H) for the optical clarity of films formed from low (LM) and high molecular (HM) weight PS particles were used to calculate the healing activation energies for the minor chains and found to be 22.0 ± 0.5 and 27.0 ± 0.6 kcal/mol, respectively. The increase in the transmitted photon intensity, I_tr, above the T_H was attributed to increase in the number of interfaces that disappeared. The Prager–Tirrell (PT) model was employed to interpret the increase in crossing density at the junction surface. The backbone activation energies (ΔE) were measured and found to be 127.8 ± 2.5 kcal/mol for a diffusing polymer chain across the junction surface for LM and HM latex films. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 866–874, 2000     

Photon transmission method for studying void‐closure kinetics during coalescence of hard latex particles

The contribution of viscous flow to void‐closure processes during film formation with hard latex particles was studied. Film optical clarity was used to follow the progress of this event. The latex films were prepared from poly (methyl methacrylate) (PMMA) particles and annealed in 10 min time intervals above the glass transition (T_g) temperature. Scanning electron microscopy (SEM) was used to detect the variation in the physical structure of the annealed films. To mimic the latex film‐formation process, Monte Carlo simulations were performed for photon transmission through the latex film and the number of transmitted and scattered photons are calculated as a function of the mean free path. A relation for transmitted light intensity, I_tr versus void closure (time)^1/2 (t^1/2) was derived by using the Vogel–Fulcher viscosity equation. The viscosity constant, B, was produced using this I_tr(t^1/2) relation at various temperatures and found to be 12.8 × 10³ K. It is shown that Monte Carlo results justified the I_tr(t^1/2) relation. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 981–988, 1999     

Reversible film formation from PS doped PNIPAM particles in various compositions

Film formation from polystyrene (PS) doped poly(N‐isopropylacrylamide) (PNIPAM) particles was studied using photon transmission technique. The transmitted light intensity, I_tr, was monitored during film formation process. Films were prepared by mixing PS and PNIPAM particles in various compositions ranging from 5 to 50 %. Samples were separately heated and cooled in constant rate at temperatures ranging from 10 to 100°C. The increase and decrease in I_tr during heating–cooling cycles were explained by void closure and void reconstruction processes. The corresponding activation energies were measured during the reversible film formation process. Percolation model was used to interpret the distribution of PS particles in PNIPAM lattice. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers     

Film formation of poly (methyl methacrylate) latex with pyrene functional poly (divinylbenzene) microspheres prepared by click chemistry

This work reports on the application of steady state fluorescence (SSF) technique for studying film formation from poly(methyl methacrylate) (PMMA) latex and poly(divinylbenzene) (PDVB) microsphere composites. Pyrene (P) functionalized PDVB cross‐linked spherical microspheres with diameters of 2.5 μm were synthesized by using precipitation polymerization technique followed by click coupling reaction. The diameter of the PMMA particles prepared by emulsion polymerization were in the range of 0.5–0.7 μm. PMMA/PDVB composite films were then prepared by physically blending of PMMA latex with PDVB microspheres at various composition (0, 1, 3, 5, 10, 20, 40, and 60 wt%). After drying, films were annealed at elevated temperatures above T_g of PMMA ranging from 100 to 270°C for 10 min time intervals. Evolution of transparency of the composite films was monitored by using photon transmission intensity, I_tr. Monomer (I_P) and excimer (I_E) fluorescence intensities from P were measured after each annealing step. The possibility of using the excimer‐to‐monomer intensity ratio (I_E/I_P) from PDVB microparticles as a measure of PMMA latex coalescence was demonstrated. Diffusion of the PMMA chains across the particle–particle interfaces dilutes the dyes, increasing their separation. The film formation stages of PMMA latexes were modeled by monitoring the I_E/I_P ratios and related activation energies were determined. There was no observable change in activation energies confirming that film formation behavior is not affected by varying the PDVB composition in the studied range. SEM images of PMMA/PDVB composites confirmed that the PMMA particles undergo complete coalescence forming a continuous phase in where PDVB microspheres are dispersed. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Temperature dependence of oxygen diffusion into polymer/carbon nanotube composite films

This study examines the transport properties of polystyrene (PS)/multiwalled carbon nanotube (MWNT) composite films taking into consideration both MWNT composition and temperature, via fluorescence technique. Three different (3, 15, and 40 wt%) MWNT content films were prepared from PS/MWNT mixtures by annealing them at 170°C, above the glass transition temperature of PS for 10 min. The diffusivity of the PS/MWNT composite was determined by performing oxygen (O₂) diffusion measurements within a temperature range of 24 to 70°C for each film and pyrene (P) was used as the fluorescent probe. The diffusion coefficients (D) of oxygen were determined by the fluorescence quenching method assuming Fickian transport. Results indicated that D values are strongly dependent on both temperature and the MWNT content in the film and it was also observed that D coefficients obey Arrhenius behavior, from which diffusion energies were produced and increased along with increases of MWNT content. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Photon transmission technique for studying film formation from polystyrene latexes prepared by dispersion polymerization using various steric stabilizers

A photon-transmission method was used to monitor the evolution of transparency during film formation from various polystyrene (PS) particles which were produced using different steric stabilizers, that is, poly(acrylic acid) (PAA), poly(vinyl alcohol) (PVA), and polyvinylpyrrolidone (PVP). The latex films were prepared from PS particles at room temperature and annealed at elevated temperatures in various time intervals above the glass transition (T_g). To simulate the latex film-formation process, a Monte Carlo technique was performed for photon transmission through a rectangular lattice. The number of transmitted (N_tr) photons were calculated as a function of particle–particle interfaces that disappeared. The increase in the transmitted photon intensity (I_tr) was attributed to the increase in the number of interfaces that disappeared. The Prager–Tirrell (PT) model was employed to interpret the increase in crossing density at the junction surface. The backbone activation energy (ΔE) was measured and found to be around 120 kcal mol⁻¹ for a diffusing polymer chain across the junction surface for all PS latex films. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1257–1267, 1998     

Effect of molecular weight on latex film formation: Photon transmission study

A UV-visible (UVV) technique was used to monitor the evolution of transparency during film formation from hard latex particles. Two different latex films were prepared from particles with high and low molecular weight (HM and LM) poly(methyl methacrylate) (PMMA) separately and annealed at elevated temperatures in various time intervals above the glass transition temperature (T_g). In both films, a continuous increase in the transmitted photon intensity (I_tr) was observed above 160°C as the annealing temperature was increased. However, the reflected photon intensity (I_rf) first decreased and then increased by showing a minimum in the same temperature range as the annealing temperature was increased. The increase in the transmitted photon intensity (I_tr) is attributed to increase in the “crossing density” at the junction surface. The activation energies for back-and-forth motion (ΔE_tr) were measured and found to be around 35 and 25 kcal/mol for the reptating polymer chain across the junction surface in the LM and HM films, respectively. The decrease in I_rf was explained by the void-closure mechanism, and the increase in the I_rf above 160°C was again attributed to the increase in the crossing density at the junction surface. Back-and-forth activation energies (ΔE_rf) were measured to be around 47 and 18 kcal/mol and the void-closure constants (B) were found to be around 24 × 10³ and 12 × 10³ K for the LM and HM film samples, respectively. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 339–351, 1998     

Fluorescence and UV techniques for studying neck growth and equilibration processes during latex film formation

Steady state fluorescence (SSF) and UV–visible techniques have been used to study neck growth and equilibration processes during the coalescence of hard latex particles. Latex films were prepared separately by annealing pyrene (P_y) labelled and unlabelled poly(methyl methacrylate) (PMMA) particles above their glass transition temperature. During the annealing processes, the optical clarity of the films increased considerably. Direct fluorescence emission of excited pyrene from labelled latex films was monitored as a function of annealing temperature to detect this change. Void closure temperature (T_c) and time (t_c) were determined at the point where the fluorescence emission intensity became maximal. Below this point, the increase in fluorescence intensity (I_op) against temperature was used to determine the activation energy for viscous flow (ΔH≈47kcalmol⁻¹). The decrease in I_op above the void closure temperature was used to determine the backbone activation energy (ΔE≈44kcalmol⁻¹) for the interdiffusing chains. Unlabelled PMMA particles were used to prepare films for UV–vis measurements. The transmitted photon intensity (I_tr) from these films increased as the annealing temperature was increased. This behaviour was also used to determine the backbone activation energy (ΔE≈35kcalmol⁻¹) for the interdiffusing chains. © Society of Chemical Industry.     

Study of film formation from PS latex/TiO2 nanocomposites; Effect of latex size and TiO2 content

In this work, we investigated the film formation from polystyrene (PS) latex/TiO₂ nanocomposites using the steady state fluorescence (SSF) and UV–vis (UVV) techniques depending on PS particle size and TiO₂ content. The structural properties of films were characterized by scanning electron microscope (SEM). The films were prepared from pyrene (P)‐labeled PS particles (SmPS:203 nm; LgPS:382 nm) by covering them with different layers of TiO₂ by dip‐coating method and then annealed at elevated temperatures. Two film series (SmPS/TiO₂ and LgPS/TiO₂) were prepared and seven different films were studied in various TiO₂ contents for each series. Scattered (I_sc), fluorescence (I_P), and transmitted (I_tr) light intensities were measured after each annealing step to monitor the stages of film formation. Results showed that, SmPS/TiO₂ films undergo complete film formation independent of TiO₂ content. However, no film formation occurs above a certain TiO₂ content in LgPS/TiO₂ films. SEM images showed that SmPS/TiO₂ films have highly well‐ordered microporous structures with increasing TiO₂ content after extraction of PS polymer whereas LgPS/TiO2 composites show no porous structure for high TiO₂ content. Our experiments also showed that porous TiO₂ films with different sizes could be successfully prepared using this technique. POLYM. COMPOS., 35:2376–2389, 2014. © 2014 Society of Plastics Engineers     

Monitoring the film formation process of polystyrene/poly acrylamide (PS/PAAm) composite films annealed by IR heating

In this study, UV‐visible (UVV) technique was used to probe the evolution of optical transmission during the film formation from composites of polystyrene (PS) latex particles and poly acrylamide (PAAm) films annealed by the infrared radiative heating (IRH) and convectional heating. Activation energies corresponding to the void closure and the interdiffusion stages were calculated. It was shown that the activation energy for the void closure processes of viscous flow from the composite films decreased considerably in IRH annealing technique. It was observed that IRH heating speeds up the film formation process and the decrease the required energy. POLYM. ENG. SCI., 58:353–360, 2018. © 2017 Society of Plastics Engineers