Branching Defects in Dendritic Molecules: Coupling Efficiency and Congestion Effects

International audienceAn analytical model supplemented by Monte Carlo simulations specifies the statistics of branching defects in dendritic molecules as a function of the generation g as well as the maximal g for which defect-free synthesis is possible, gmax. The defects arise because of (i) imperfect coupling efficiency characterized by a constant fraction P ≤ 1 of successful add-on reactions in the absence of excluded volume effects and (ii) packing constraints associated with steric congestion at high g when the maximal density is approached. The model specifies ng, the number of junctions, and the number of defects for both g ≤ gmax and g > gmax, as well as gmax and its dependence on P. The branching polydispersity is characterized by the average number of junction-junction bonds, Xgeff. For g gmax, branching is strongly reduced, and Xgeff slowly approaches 2 as Xgeff - 2 1/g while ng eventually exhibits power law growth: ng g3 for dendrimers and ng g2 for dendronized polymers. The branching defects can be interrogated by different forms of end-group analysis utilizing the theory framework proposed

Measurement of the np -> np pi(0)pi(0) reaction in search for the recently observed d* (2380) resonance

Exclusive measurements of the quasi-free np --> np pi(0)pi(0) reaction have been performed by means of dp collisions at T-d = 2.27 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region root s = (2.35-2.46) GeV, which includes the region of the ABC effect and its associated d* (2380) resonance. Adding the d* resonance amplitude to that for the conventional processes leads to a reasonable description of the data. The observed resonance effect in the total cross section is in agreement with the predictions of Faldt and Wilkin as well with those of Albadajedo and Oset. The ABC effect, i.e. the low-mass enhancement in the pi(0)pi(0)-invariant mass spectrum, is found to be very modest - if present at all, which might pose a problem to some of its interpretations

Measurement of the np -> np pi(0)pi(0) reaction in search for the recently observed d* (2380) resonance

Exclusive measurements of the quasi-free np --> np pi(0)pi(0) reaction have been performed by means of dp collisions at T-d = 2.27 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region root s = (2.35-2.46) GeV, which includes the region of the ABC effect and its associated d* (2380) resonance. Adding the d* resonance amplitude to that for the conventional processes leads to a reasonable description of the data. The observed resonance effect in the total cross section is in agreement with the predictions of Faldt and Wilkin as well with those of Albadajedo and Oset. The ABC effect, i.e. the low-mass enhancement in the pi(0)pi(0)-invariant mass spectrum, is found to be very modest - if present at all, which might pose a problem to some of its interpretations

Measurement of the np -> np pi(0)pi(0) reaction in search for the recently observed d* (2380) resonance

Exclusive measurements of the quasi-free np --> np pi(0)pi(0) reaction have been performed by means of dp collisions at T-d = 2.27 GeV using the WASA detector setup at COSY. Total and differential cross sections have been obtained covering the energy region root s = (2.35-2.46) GeV, which includes the region of the ABC effect and its associated d* (2380) resonance. Adding the d* resonance amplitude to that for the conventional processes leads to a reasonable description of the data. The observed resonance effect in the total cross section is in agreement with the predictions of Faldt and Wilkin as well with those of Albadajedo and Oset. The ABC effect, i.e. the low-mass enhancement in the pi(0)pi(0)-invariant mass spectrum, is found to be very modest - if present at all, which might pose a problem to some of its interpretations