Using an approximation scheme within the convective diffusion (two-body Smoluchowski) equation framework, we unveil the shear-driven aggregation mechanism at the origin of structure formation in sheared colloidal systems. The theory, verified against numerics and experiments, explains the induction time followed by explosive (irreversible) rise of viscosity observed in charge-stabilized colloidal and protein systems under steady shear. The Arrhenius-type equation with shear derived here, extending Kramers' theory in the presence of shear, clearly demonstrates the important role of shear drive in activated-rate processes as they are encountered in soft condensed matter.

The manufacturing of recombinant protein is traditionally divided in two main steps: upstream (cell culture and synthesis of the target protein) and downstream (purification and formulation of the protein into a drug substance or drug product). Today, cost pressure, market uncertainty and market growth, challenge the existing manufacturing technologies. Leaders in the field are active in designing the process of the future and continuous manufacturing is recurrently mentioned as a potential solution to address some of the current limitations. This review focuses on the application of continuous processing to the first step of the manufacturing process. Enabling technologies and operation modes are described in the first part. In the second part, recent advances in the field that have the potential to support its successful future development are critically discussed.

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The ring-opening polymerization of l,l-lactide with 2-ethylhexanoic acid tin(II) salt as catalyst, and 1-dodecanol as cocatalyst, is investigated at temperatures ranging from 140 to 180 °C and various operating conditions such as different ratios of monomer to catalyst as well as catalyst to cocatalyst amounts. Average molecular weights and byproduct formation have been measured as a function of monomer conversion. A complete kinetic model including intra- and intermolecular transesterifications as well as random chain scission has been developed. All experimental data have been compared with the predictions of the model, which is coherent with the one developed for lower temperature values in a previous work [Yu, Y. C.; Storti, G.; Morbidelli, M. Macromolecules 2009, 42, 8187]. This results in a reliable estimation of the rate coefficients of all involved reactions in a relatively large range of temperatures (130–180 °C).

Ring-opening polymerization of L,L-lactide with various amounts of catalyst, 2-ethylhexanoic acid tin(II) salt, and cocatalyst, 1-dodecanol, at 130 °C in bulk is examined. Monomer-to-catalyst and cocatalyst-to-catalyst molar ratios were changed from 500 to 4000 and from 1 to 600, respectively. In agreement with previous literature, the catalyst concentration is affecting the reaction rate, whereas OHbearing species (such as cocatalyst and impurities) are controlling both reaction rate and polymer molecular weight. A model implementing a living kinetic scheme is first developed and validated by comparison with the experimental results. The rate coefficients of the main reactions (activation, propagation, and reversible chain transfer) have been evaluated. Finally, to predict with accuracy the broadening of the molecular weight distribution, we introduce ester interchange reactions, so-called "transesterifications", into the kinetic scheme, and the corresponding rate coefficient is evaluated.

Polyethylene furanoate (PEF) represents a promising renewable resource-based bioplastic as replacement for fossil-based polyethylene terephthalate (PET) with improved material properties. However, the synthesis of PEF through conventional polycondensation remains challenging, since the time-intensive reaction leads to degradation and undesired discolouration of the product. Here we show the successful rapid synthesis of bottle-grade PEF via ring-opening polymerisation (ROP) from cyclic PEF oligomers within minutes, thereby avoiding degradation and discolouration. The melting point of such mixture of cyclic oligomers lies around 370 °C, well above the degradation temperature of PEF (~329 °C). This challenge can be overcome, exploiting the self-plasticising effect of the forming polymer itself (which melts around 220 °C) by initiation in the presence of a high boiling, yet removable, and inert liquid plasticiser. This concept yields polymer grades required for bottle applications (Mn > 30 kg mol−1, conversion > 95%, colour-free products), and can be extended to other diffusion-limited polymer systems.

a b s t r a c tThe present work aims at reviewing our current understanding of fractal structures in the frame of colloid aggregation as well as the possibility they offer to produce novel structured materials. In particular, the existing techniques to measure and compute the fractal dimension d f are critically discussed based on the cases of organic/inorganic particles and proteins. Then the aggregation conditions affecting d f are thoroughly analyzed, pointing out the most recent literature findings and the limitations of our current understanding. Finally, the importance of the fractal dimension in applications is discussed along with possible directions for the production of new structured materials.

The breakup of dense aggregates in an extensional flow was investigated experimentally. The flow was realized by pumping the suspension containing the aggregates through a contracting nozzle. Variation of the cluster mass distribution during the breakage process was measured by small-angle light scattering. Because of the large size of primary particles and the dense aggregate structure image analysis was used to determine the shape and structure of the produced fragments. It was found, that neither aggregate structure, characterized by a fractal dimension d(f) = 2.7, nor shape, characterized by an average aspect ratio equal to 1.5, was affected by breakage. Several passes through the nozzle were required to reach the steady state. This is explained by the radial variation of the hydrodynamic stresses at the nozzle entrance, characterized through computational fluid dynamics, which implies that only the fraction of aggregates whose strength is smaller than the local hydrodynamic stress is broken during one pass through the nozzle. Scaling of the steady-state aggregate size as a function of the hydrodynamic stress was used to determine the aggregate strength.