Thermodynamics of swelling of latex particles with two monomers

The partitioning of 2 monomers between the latex particle, monomer droplet, and aq. phases of an emulsion polymer latex are measured at satn. swelling of the latex particle phase (corresponding to intervals I and II of an emulsion polymn.). The monomer (Me acrylate, Bu acrylate, styrene) and polymer of these expts. correspond well to a simplified thermodn. theory of the satn. swelling of an emulsion polymer with 2 monomers, in which it is realized that the fraction of 1 monomer is equiv. in the latex particle and monomer droplet phases. Henry's law holds for monomers, both in the absence and in the presence of swollen latex particles. A simple empirical relation is developed whereby the concn. of 2 monomers at any ratio can be calcd. from the individual satn. concn. of the 2 monomers in the latex of interes

Partial swelling of latex particles with monomers

Two methods are described for exptl. detg. the concns. of monomer in both the aq. phase and the latex particle phase during partial swelling of latex particles, and therefore also during interval III of an emulsion polymn. The ratio of the monomer concns. in the aq. phase, both below and at satn., can be related to the vol. fraction of polymer in the latex particles via the Vanzo equation. Comparison of theory and expts. for the Me acrylate and Me acrylate-styrene copolymer systems shows that the monomer partitioning is insensitive to temp., latex particle radius, polymer compn., polymer mol. wt., and polymer crosslinking. Thermodn. treatment of these and previously published partitioning results shows, at high vol. fractions of polymer, that the conformational entropy of mixing of monomer and polymer is the significant term detg. the degree of partial latex particle swelling by monomer. Theor. predictions of exptl. results are quite insensitive to values of the Flory-Huggins interaction parameter and to the latex particle-water interfacial tension. A simple model is developed for the estn. of monomer partitioning which requires only the satn. monomer concns. in the particle and aq. phase

Adaptive Biosensing and Neuromorphic Classification Based on an Ambipolar Organic Mixed Ionic–Electronic Conductor

Organic mixed ionic–electronic conductors (OMIECs) are central to bioelectronic applications such as biosensors, health-monitoring devices, and neural interfaces, and have facilitated efficient next-generation brain-inspired computing and biohybrid systems. Despite these examples, smart and adaptive circuits that can locally process and optimize biosignals have not yet been realized. Here, a tunable sensing circuit is shown that can locally modulate biologically relevant signals like electromyograms (EMGs) and electrocardiograms (ECGs), that is based on a complementary logic inverter combined with a neuromorphic memory element, and that is constructed from a single polymer mixed conductor. It is demonstrated that a small neuromorphic array based on this material effects high classification accuracy in heartbeat anomaly detection. This high-performance material allows for straightforward monolithic integration, which reduces fabrication complexity while also achieving high on/off ratios with excellent ambient p- and n-type stability in transistor performance. This material opens a route toward simple and straightforward fabrication and integration of more sophisticated adaptive circuits for future smart bioelectronics

High-Performance Organic Electrochemical Transistors and Neuromorphic Devices Comprising Naphthalenediimide-Dialkoxybithiazole Copolymers Bearing Glycol Ether Pendant Groups

Organic electrochemical transistors (OECTs) have emerged as building blocks for low power circuits, biosensors, and neuromorphic computing. While p-type polymer materials for OECTs are well developed, the choice of high-performance n-type polymers is limited, despite being essential for cation and metabolite biosensors, and crucial for constructing complementary circuits. N-type conjugated polymers that have efficient ion-to-electron transduction are highly desired for electrochemical applications. In this contribution, three non-fused, planar naphthalenediimide (NDI)-dialkoxybithiazole (2Tz) copolymers, which systematically increase the amount of polar tri(ethylene glycol) (TEG) side chains: PNDI2OD-2Tz (0 TEG), PNDIODTEG-2Tz (1 TEG), PNDI2TEG-2Tz (2 TEG), are reported. It is demonstrated that the OECT performance increases with the number of TEG side chains resulting from the progressively higher hydrophilicity and larger electron affinities. Benefiting from the high electron mobility, excellent ion conduction capability, efficient ion-to-electron transduction, and low-lying lowest unoccupied molecular orbital energy level, the 2 TEG polymer achieves close to 105 on-off ratio, fast switching, 1000 stable operation cycles in aqueous electrolyte, and has a long shelf life. Moreover, the higher number TEG chain substituted polymer exhibits good conductance state retention over two orders of magnitudes in electrochemical resistive random-access memory devices, highlighting its potential for neuromorphic computing